diff --git a/apps/as/middleware.ts b/apps/as/middleware.ts
index 0b7be3348..94a1d0381 100644
--- a/apps/as/middleware.ts
+++ b/apps/as/middleware.ts
@@ -1,6 +1,6 @@
 import { NextRequest, NextResponse } from "next/server";
 
-import { PORT, PROXY_HOST, SERVER_API_URL, SITE_ID } from "@/shared/config";
+import { AUTH_USER_ID, CLAIM_NAME, PORT, PROXY_HOST, SERVER_API_URL, SITE_ID } from "@/shared/config";
 
 const serverApiUrl = process.env.SERVER_API_URL;
 
@@ -34,6 +34,28 @@ export function middleware(req: NextRequest) {
     return addSecurityHeaders(response);
   }
 
+  
+  // tus-js-client PATCH 요청: Location 헤더로 /server 없이 반환된 경로 직접 처리
+  // (예: /attach-service/api/v1/tus/upload/{id})
+  if (pathname.startsWith("/attach-service")) {
+    const requestHeaders = new Headers(req.headers);
+    const token = req.cookies.get(CLAIM_NAME)?.value;
+    const userId = req.cookies.get(AUTH_USER_ID)?.value;
+    const newUrl = `${serverApiUrl}${pathname}`;
+
+    if (token) requestHeaders.set(CLAIM_NAME, token);
+    if (userId) requestHeaders.set(AUTH_USER_ID, userId);
+
+    logMessages.push(`  [TUS Proxy] Rewritten URL: ${newUrl}`);
+    logMessages.push("\n--------------------------------\n");
+    console.log(logMessages.join("\n"));
+
+    const response = NextResponse.rewrite(new URL(newUrl), {
+      headers: requestHeaders,
+    });
+    return addSecurityHeaders(response);
+  }
+
   // if (pathname === "/") {
   //   const response = NextResponse.redirect(new URL("/dashboard", req.url));
   //   return addSecurityHeaders(response);
@@ -47,5 +69,5 @@ export function middleware(req: NextRequest) {
 }
 
 export const config = {
-  matcher: ["/server/:path*", "/"],
+  matcher: ["/server/:path*", "/attach-service/:path*", "/"],
 };
diff --git a/apps/as/src/pages/instl-sncn/ui/cnfm-regist-page.tsx b/apps/as/src/pages/instl-sncn/ui/cnfm-regist-page.tsx
index e7f2e1261..6424f9f17 100644
--- a/apps/as/src/pages/instl-sncn/ui/cnfm-regist-page.tsx
+++ b/apps/as/src/pages/instl-sncn/ui/cnfm-regist-page.tsx
@@ -4,9 +4,10 @@ import { useEffect, useMemo, useRef, useState } from "react";
 import { useRouter } from "next/navigation";
 
 import { useQuery } from "@tanstack/react-query";
+import axios from "axios";
 import { type HttpResponse,Upload } from "tus-js-client";
 
-import { AUTH_USER_ID, CLAIM_NAME, ENDPOINT } from "@/shared/config";
+import { AUTH_USER_ID, CLAIM_NAME, ENDPOINT, PROXY_HOST } from "@/shared/config";
 import { getCookie, setCookie } from "@/shared/lib";
 import type { AcntgSeMngTreeDto } from "@/entities/acntg";
 import { acntgService } from "@/entities/acntg";
@@ -173,7 +174,7 @@ function CnfmRegistPage() {
     setCookie("atfl-cd-key", "");
 
     const upload = new Upload(file, {
-      endpoint: ENDPOINT.ATTACH_SERVICE.TUS_UPLOAD,
+      endpoint: `${PROXY_HOST}${ENDPOINT.ATTACH_SERVICE.TUS_UPLOAD}`,
       chunkSize: 10 * 1024 * 1024,
       headers: {
         [CLAIM_NAME]: getCookie(CLAIM_NAME) ?? "",
@@ -575,7 +576,11 @@ function CnfmRegistPage() {
       alert(`저장되었습니다. 문서번호: ${issuedDocNo}`);
     } catch (error) {
       console.error("저장 API 호출 실패", error);
-      alert("저장 중 오류가 발생했습니다.");
+      const serverMessage =
+        axios.isAxiosError(error) && error.response?.data?.message
+          ? (error.response.data as { message: string }).message
+          : "저장 중 오류가 발생했습니다.";
+      alert(serverMessage);
     }
   }