diff --git a/src/main/java/com/sb/web/board/controller/BoardImageController.java b/src/main/java/com/sb/web/board/controller/BoardImageController.java
index 5fa45a1..70ba315 100644
--- a/src/main/java/com/sb/web/board/controller/BoardImageController.java
+++ b/src/main/java/com/sb/web/board/controller/BoardImageController.java
@@ -6,6 +6,7 @@ import com.sb.web.board.domain.BoardImage;
 import com.sb.web.board.service.BoardImageService;
 import com.sb.web.common.exception.ApiException;
 import lombok.RequiredArgsConstructor;
+import org.springframework.beans.factory.annotation.Value;
 import org.springframework.http.CacheControl;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
@@ -28,6 +29,10 @@ public class BoardImageController {
 
     private final BoardImageService service;
 
+    // 앱(Capacitor) 출처가 localhost 라 상대경로가 안 통하므로 절대 URL 로 반환
+    @Value("${app.public-url:}")
+    private String publicUrl;
+
     @PostMapping("/api/board/images")
     public Map<String, String> upload(
             @RequestParam("image") MultipartFile file,
@@ -40,7 +45,8 @@ public class BoardImageController {
             throw new ApiException(HttpStatus.BAD_REQUEST, "이미지 파일만 업로드할 수 있습니다.");
         }
         Long id = service.save(current.getId(), contentType, file.getBytes());
-        return Map.of("url", "/api/images/" + id);
+        String base = (publicUrl == null) ? "" : publicUrl.replaceAll("/+$", "");
+        return Map.of("url", base + "/api/images/" + id);
     }
 
     @GetMapping("/api/images/{id}")
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
index 85e9e6c..c2cef91 100644
--- a/src/main/resources/application.yml
+++ b/src/main/resources/application.yml
@@ -74,6 +74,8 @@ google:
 app:
   crypto:
     account-key: ${ACCOUNT_CRYPTO_KEY:}
+  # 업로드 이미지 등 외부에서 접근할 절대 URL 베이스. 앱(Capacitor)은 출처가 localhost 라 상대경로가 안 통함.
+  public-url: ${PUBLIC_URL:https://app.sblog.kr}
 
 # ===== Logging =====
 logging: