diff --git a/src/main/java/com/gcsc/connection/apikey/dto/ApiKeyRequestReviewDto.java b/src/main/java/com/gcsc/connection/apikey/dto/ApiKeyRequestReviewDto.java
index 9daad38..7c38a28 100644
--- a/src/main/java/com/gcsc/connection/apikey/dto/ApiKeyRequestReviewDto.java
+++ b/src/main/java/com/gcsc/connection/apikey/dto/ApiKeyRequestReviewDto.java
@@ -9,6 +9,7 @@ public record ApiKeyRequestReviewDto(
     String reviewComment,
     List<Long> adjustedApiIds,
     String adjustedFromDate,
-    String adjustedToDate
+    String adjustedToDate,
+    Long adjustedDailyRequestLimit
 ) {
 }
diff --git a/src/main/java/com/gcsc/connection/apikey/dto/CreateApiKeyRequest.java b/src/main/java/com/gcsc/connection/apikey/dto/CreateApiKeyRequest.java
index ded5744..3f4680f 100644
--- a/src/main/java/com/gcsc/connection/apikey/dto/CreateApiKeyRequest.java
+++ b/src/main/java/com/gcsc/connection/apikey/dto/CreateApiKeyRequest.java
@@ -3,6 +3,7 @@ package com.gcsc.connection.apikey.dto;
 import jakarta.validation.constraints.NotBlank;
 
 public record CreateApiKeyRequest(
-    @NotBlank String keyName
+    @NotBlank String keyName,
+    Long dailyRequestLimit
 ) {
 }
diff --git a/src/main/java/com/gcsc/connection/apikey/entity/SnpApiKey.java b/src/main/java/com/gcsc/connection/apikey/entity/SnpApiKey.java
index 31f627c..81bca80 100644
--- a/src/main/java/com/gcsc/connection/apikey/entity/SnpApiKey.java
+++ b/src/main/java/com/gcsc/connection/apikey/entity/SnpApiKey.java
@@ -60,10 +60,13 @@ public class SnpApiKey extends BaseEntity {
     @Column(name = "last_used_at")
     private LocalDateTime lastUsedAt;
 
+    @Column(name = "daily_request_limit")
+    private Long dailyRequestLimit;
+
     @Builder
     public SnpApiKey(SnpUser user, String apiKey, String apiKeyPrefix, String keyName,
                      ApiKeyStatus status, SnpUser approvedBy, LocalDateTime approvedAt,
-                     LocalDateTime expiresAt) {
+                     LocalDateTime expiresAt, Long dailyRequestLimit) {
         this.user = user;
         this.apiKey = apiKey;
         this.apiKeyPrefix = apiKeyPrefix;
@@ -72,6 +75,7 @@ public class SnpApiKey extends BaseEntity {
         this.approvedBy = approvedBy;
         this.approvedAt = approvedAt;
         this.expiresAt = expiresAt;
+        this.dailyRequestLimit = dailyRequestLimit;
     }
 
     public void revoke() {
diff --git a/src/main/java/com/gcsc/connection/apikey/service/ApiKeyRequestService.java b/src/main/java/com/gcsc/connection/apikey/service/ApiKeyRequestService.java
index 359fff8..b9db92b 100644
--- a/src/main/java/com/gcsc/connection/apikey/service/ApiKeyRequestService.java
+++ b/src/main/java/com/gcsc/connection/apikey/service/ApiKeyRequestService.java
@@ -150,6 +150,11 @@ public class ApiKeyRequestService {
         String prefix = rawKey.substring(0, PREFIX_LENGTH);
         String encryptedKey = aesEncryptor.encrypt(rawKey);
 
+        // 일일 요청 제한: 검토자가 조정한 값 > 신청자 입력값 > null(무제한)
+        Long dailyLimit = dto.adjustedDailyRequestLimit() != null
+            ? dto.adjustedDailyRequestLimit()
+            : request.getDailyRequestEstimate();
+
         SnpApiKey apiKey = SnpApiKey.builder()
             .user(request.getUser())
             .apiKey(encryptedKey)
@@ -159,6 +164,7 @@ public class ApiKeyRequestService {
             .approvedBy(reviewer)
             .approvedAt(LocalDateTime.now())
             .expiresAt(request.getUsageToDate())
+            .dailyRequestLimit(dailyLimit)
             .build();
 
         SnpApiKey savedKey = snpApiKeyRepository.save(apiKey);
diff --git a/src/main/java/com/gcsc/connection/apikey/service/ApiKeyService.java b/src/main/java/com/gcsc/connection/apikey/service/ApiKeyService.java
index e291802..8c8df77 100644
--- a/src/main/java/com/gcsc/connection/apikey/service/ApiKeyService.java
+++ b/src/main/java/com/gcsc/connection/apikey/service/ApiKeyService.java
@@ -75,6 +75,7 @@ public class ApiKeyService {
             .apiKeyPrefix(prefix)
             .keyName(request.keyName())
             .status(ApiKeyStatus.ACTIVE)
+            .dailyRequestLimit(request.dailyRequestLimit())
             .build();
 
         SnpApiKey saved = snpApiKeyRepository.save(apiKey);
diff --git a/src/main/java/com/gcsc/connection/common/dto/ApiResponse.java b/src/main/java/com/gcsc/connection/common/dto/ApiResponse.java
index 434b34f..3ba6b19 100644
--- a/src/main/java/com/gcsc/connection/common/dto/ApiResponse.java
+++ b/src/main/java/com/gcsc/connection/common/dto/ApiResponse.java
@@ -10,6 +10,7 @@ import lombok.Getter;
 public class ApiResponse<T> {
 
     private final boolean success;
+    private final String code;
     private final String message;
     private final T data;
 
@@ -34,4 +35,12 @@ public class ApiResponse<T> {
             .message(message)
             .build();
     }
+
+    public static <T> ApiResponse<T> error(String code, String message) {
+        return ApiResponse.<T>builder()
+            .success(false)
+            .code(code)
+            .message(message)
+            .build();
+    }
 }
diff --git a/src/main/java/com/gcsc/connection/common/exception/ErrorCode.java b/src/main/java/com/gcsc/connection/common/exception/ErrorCode.java
index 31496a5..a1585d7 100644
--- a/src/main/java/com/gcsc/connection/common/exception/ErrorCode.java
+++ b/src/main/java/com/gcsc/connection/common/exception/ErrorCode.java
@@ -31,6 +31,7 @@ public enum ErrorCode {
     GATEWAY_SERVICE_INACTIVE(503, "GW004", "비활성 서비스입니다"),
     GATEWAY_PERMISSION_DENIED(403, "GW005", "해당 API에 대한 권한이 없습니다"),
     GATEWAY_PROXY_FAILED(502, "GW006", "서비스 요청에 실패했습니다"),
+    GATEWAY_DAILY_LIMIT_EXCEEDED(429, "GW007", "일일 최대 호출 건수 제한으로 사용할 수 없습니다"),
     INTERNAL_ERROR(500, "SYS001", "시스템 오류가 발생했습니다");
 
     private final int status;
diff --git a/src/main/java/com/gcsc/connection/common/exception/GlobalExceptionHandler.java b/src/main/java/com/gcsc/connection/common/exception/GlobalExceptionHandler.java
index 57e1014..bb25fa5 100644
--- a/src/main/java/com/gcsc/connection/common/exception/GlobalExceptionHandler.java
+++ b/src/main/java/com/gcsc/connection/common/exception/GlobalExceptionHandler.java
@@ -26,7 +26,7 @@ public class GlobalExceptionHandler {
         log.warn("Business exception: {} - {}", errorCode.getCode(), errorCode.getMessage());
         return ResponseEntity
             .status(errorCode.getStatus())
-            .body(ApiResponse.error(errorCode.getMessage()));
+            .body(ApiResponse.error(errorCode.getCode(), errorCode.getMessage()));
     }
 
     /**
diff --git a/src/main/java/com/gcsc/connection/gateway/controller/GatewayController.java b/src/main/java/com/gcsc/connection/gateway/controller/GatewayController.java
index 3f03b7b..173871a 100644
--- a/src/main/java/com/gcsc/connection/gateway/controller/GatewayController.java
+++ b/src/main/java/com/gcsc/connection/gateway/controller/GatewayController.java
@@ -37,7 +37,7 @@ public class GatewayController {
             String remainingPath = extractRemainingPath(serviceCode, request);
             return gatewayService.proxyRequest(serviceCode, remainingPath, request);
         } catch (BusinessException e) {
-            return buildErrorResponse(e.getErrorCode().getStatus(), e.getErrorCode().getMessage());
+            return buildErrorResponse(e.getErrorCode().getStatus(), e.getErrorCode().getCode(), e.getErrorCode().getMessage());
         }
     }
 
@@ -60,8 +60,8 @@ public class GatewayController {
     /**
      * Gateway 소비자용 JSON 에러 응답 생성
      */
-    private ResponseEntity<byte[]> buildErrorResponse(int status, String message) {
-        String json = "{\"success\":false,\"message\":\"" + escapeJson(message) + "\"}";
+    private ResponseEntity<byte[]> buildErrorResponse(int status, String code, String message) {
+        String json = "{\"success\":false,\"code\":\"" + escapeJson(code) + "\",\"message\":\"" + escapeJson(message) + "\"}";
         return ResponseEntity.status(status)
             .contentType(MediaType.APPLICATION_JSON)
             .body(json.getBytes());
diff --git a/src/main/java/com/gcsc/connection/gateway/service/GatewayService.java b/src/main/java/com/gcsc/connection/gateway/service/GatewayService.java
index fcd50ec..828fa9b 100644
--- a/src/main/java/com/gcsc/connection/gateway/service/GatewayService.java
+++ b/src/main/java/com/gcsc/connection/gateway/service/GatewayService.java
@@ -8,6 +8,7 @@ import com.gcsc.connection.common.exception.BusinessException;
 import com.gcsc.connection.common.exception.ErrorCode;
 import com.gcsc.connection.common.util.AesEncryptor;
 import com.gcsc.connection.monitoring.entity.SnpApiRequestLog;
+import com.gcsc.connection.monitoring.repository.SnpApiRequestLogRepository;
 import com.gcsc.connection.monitoring.service.RequestLogService;
 import com.gcsc.connection.service.entity.SnpService;
 import com.gcsc.connection.service.entity.SnpServiceApi;
@@ -23,6 +24,7 @@ import org.springframework.stereotype.Service;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.reactive.function.client.WebClientResponseException;
 
+import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.util.Enumeration;
 import java.util.List;
@@ -34,8 +36,9 @@ import java.util.Set;
 public class GatewayService {
 
     private static final int API_KEY_PREFIX_LENGTH = 8;
+    private static final String AUTH_KEY_PARAM = "authKey";
     private static final Set<String> EXCLUDED_HEADERS = Set.of(
-        "host", "x-api-key", "connection", "content-length"
+        "host", "connection", "content-length"
     );
 
     private final SnpApiKeyRepository snpApiKeyRepository;
@@ -45,6 +48,7 @@ public class GatewayService {
     private final AesEncryptor aesEncryptor;
     private final WebClient webClient;
     private final RequestLogService requestLogService;
+    private final SnpApiRequestLogRepository snpApiRequestLogRepository;
 
     /**
      * API Gateway 프록시 요청 처리
@@ -70,8 +74,8 @@ public class GatewayService {
             // 2. 대상 URL 조합 (실패 로그에도 사용)
             targetUrl = buildTargetUrl(service.getServiceUrl(), remainingPath, request);
 
-            // 3. API Key 추출
-            String rawKey = request.getHeader("X-API-KEY");
+            // 3. API Key 추출 (쿼리 파라미터 authKey)
+            String rawKey = request.getParameter(AUTH_KEY_PARAM);
             if (rawKey == null || rawKey.isBlank()) {
                 throw new BusinessException(ErrorCode.GATEWAY_API_KEY_MISSING);
             }
@@ -82,7 +86,10 @@ public class GatewayService {
             // 5. Key 상태/만료 검증
             validateApiKey(apiKey);
 
-            // 6. ServiceApi 조회 (경로 + 메서드 매칭, {변수} 패턴 지원)
+            // 6. 일일 요청량 제한 검증
+            validateDailyLimit(apiKey);
+
+            // 7. ServiceApi 조회 (경로 + 메서드 매칭, {변수} 패턴 지원)
             String apiPath = remainingPath.startsWith("/") ? remainingPath : "/" + remainingPath;
             SnpServiceApi serviceApi = matchServiceApi(service.getServiceId(), apiPath, request.getMethod());
 
@@ -109,7 +116,8 @@ public class GatewayService {
 
         } catch (BusinessException e) {
             int responseTime = (int) (System.currentTimeMillis() - startTime);
-            saveLog(request, service, apiKey, targetUrl, gatewayPath, "FAIL",
+            String logStatus = isDeniedError(e.getErrorCode()) ? "DENIED" : "FAIL";
+            saveLog(request, service, apiKey, targetUrl, gatewayPath, logStatus,
                 e.getErrorCode().getStatus(), responseTime, 0L,
                 e.getErrorCode().getMessage(), requestedAt);
             throw e;
@@ -192,6 +200,36 @@ public class GatewayService {
         }
     }
 
+    private static final Set<ErrorCode> DENIED_ERROR_CODES = Set.of(
+        ErrorCode.GATEWAY_API_KEY_MISSING,
+        ErrorCode.GATEWAY_API_KEY_INVALID,
+        ErrorCode.GATEWAY_API_KEY_EXPIRED,
+        ErrorCode.GATEWAY_PERMISSION_DENIED,
+        ErrorCode.GATEWAY_DAILY_LIMIT_EXCEEDED
+    );
+
+    private boolean isDeniedError(ErrorCode errorCode) {
+        return DENIED_ERROR_CODES.contains(errorCode);
+    }
+
+    /**
+     * 일일 요청량 제한 검증
+     */
+    private void validateDailyLimit(SnpApiKey apiKey) {
+        Long limit = apiKey.getDailyRequestLimit();
+        if (limit == null) {
+            return;
+        }
+
+        LocalDateTime startOfDay = LocalDate.now().atStartOfDay();
+        long todayCount = snpApiRequestLogRepository
+            .countByApiKeyApiKeyIdAndRequestedAtGreaterThanEqual(apiKey.getApiKeyId(), startOfDay);
+
+        if (todayCount >= limit) {
+            throw new BusinessException(ErrorCode.GATEWAY_DAILY_LIMIT_EXCEEDED);
+        }
+    }
+
     /**
      * 대상 URL 구성
      */
@@ -206,7 +244,13 @@ public class GatewayService {
 
         String queryString = request.getQueryString();
         if (queryString != null && !queryString.isEmpty()) {
-            url.append("?").append(queryString);
+            // authKey 파라미터는 프록시 대상에 전달하지 않음
+            String filtered = java.util.Arrays.stream(queryString.split("&"))
+                .filter(p -> !p.startsWith(AUTH_KEY_PARAM + "="))
+                .collect(java.util.stream.Collectors.joining("&"));
+            if (!filtered.isEmpty()) {
+                url.append("?").append(filtered);
+            }
         }
 
         return url.toString();
@@ -327,9 +371,7 @@ public class GatewayService {
         Enumeration<String> headerNames = request.getHeaderNames();
         while (headerNames.hasMoreElements()) {
             String name = headerNames.nextElement();
-            if (!"x-api-key".equalsIgnoreCase(name)) {
-                sb.append(name).append(": ").append(request.getHeader(name)).append("\n");
-            }
+            sb.append(name).append(": ").append(request.getHeader(name)).append("\n");
         }
         return sb.toString();
     }
diff --git a/src/main/java/com/gcsc/connection/monitoring/repository/SnpApiRequestLogRepository.java b/src/main/java/com/gcsc/connection/monitoring/repository/SnpApiRequestLogRepository.java
index bff32e8..9d54bae 100644
--- a/src/main/java/com/gcsc/connection/monitoring/repository/SnpApiRequestLogRepository.java
+++ b/src/main/java/com/gcsc/connection/monitoring/repository/SnpApiRequestLogRepository.java
@@ -12,6 +12,9 @@ import java.util.List;
 public interface SnpApiRequestLogRepository extends JpaRepository<SnpApiRequestLog, Long>,
     JpaSpecificationExecutor<SnpApiRequestLog> {
 
+    /** API Key별 일일 요청 건수 */
+    long countByApiKeyApiKeyIdAndRequestedAtGreaterThanEqual(Long apiKeyId, LocalDateTime startOfDay);
+
     /** 오늘 요약: 총 요청, 성공 건수, 평균 응답시간 */
     @Query(value = "SELECT COUNT(*) as total, " +
         "COUNT(CASE WHEN request_status = 'SUCCESS' THEN 1 END) as successCount, " +