diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
index a67342f..b31a113 100644
--- a/.github/PULL_REQUEST_TEMPLATE.md
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -1,3 +1,5 @@
+<!--PR 제목에 "@coderabbitai 제목" 이 들어있으면 CodeRabbit이 자동으로 제목을 생성해줍니다!-->
+
 ## 💻 작업 내용
 
 <!--구현한 내용을 설명해주세요.-->
diff --git a/src/app/App.tsx b/src/app/App.tsx
index b80f1d8..95a2a52 100644
--- a/src/app/App.tsx
+++ b/src/app/App.tsx
@@ -1,10 +1,6 @@
-import { useState } from 'react';
+import { useEffect } from 'react';
 import { ThemeProvider } from 'styled-components';
-import {
-  QueryCache,
-  QueryClient,
-  QueryClientProvider,
-} from '@tanstack/react-query';
+import { QueryClientProvider } from '@tanstack/react-query';
 import GlobalStyles from '@/shared/styles/globalStyles';
 import theme from '@/shared/styles/theme';
 import AppRouter from '@/app/Router';
@@ -12,29 +8,18 @@ import { ReactQueryDevtools } from '@tanstack/react-query-devtools';
 import GlobalErrorBoundary from '@/app/GlobalErrorBoundary';
 import Toast from '@/shared/ui/Toast';
 import useApiError from '@/shared/hooks/useApiError';
+import { queryClient, setupQueryClient } from '@/shared/api/queryClient';
 import Layout from './Layout';
 import 'react-toastify/dist/ReactToastify.css';
 
 function App() {
   const { handleError: handleQueryError } = useApiError({});
   const { handleError: handleMutationError } = useApiError({});
-  const [queryClient] = useState(
-    () =>
-      new QueryClient({
-        defaultOptions: {
-          mutations: {
-            onError: handleMutationError,
-            throwOnError: true, // 기본적으로 RouteErrorBoundary로 에러를 던집니다.
-          },
-          queries: {
-            throwOnError: true, // 기본적으로 RouteErrorBoundary로 에러를 던집니다.
-          },
-        },
-        queryCache: new QueryCache({
-          onError: handleQueryError,
-        }),
-      })
-  );
+
+  useEffect(() => {
+    setupQueryClient(handleQueryError, handleMutationError);
+  }, [handleMutationError, handleQueryError]);
+
   return (
     <ThemeProvider theme={theme}>
       <GlobalErrorBoundary>
diff --git a/src/app/Router.tsx b/src/app/Router.tsx
index 39e08cb..6f1cfff 100644
--- a/src/app/Router.tsx
+++ b/src/app/Router.tsx
@@ -52,10 +52,12 @@ const NotFound = lazy(() =>
 function AppRouter() {
   const router = createBrowserRouter([
     {
-      path: '',
+      id: 'root',
       element: (
         <RouteErrorBoundary>
-          <Outlet />
+          <Suspense fallback={<div>loading...</div>}>
+            <Outlet />
+          </Suspense>
         </RouteErrorBoundary>
       ),
       errorElement: <RouteErrorElement />,
@@ -65,24 +67,29 @@ function AppRouter() {
           element: <Login />,
         },
         {
-          path: ROUTE.onboarding,
-          element: <Onboarding />,
-        },
-        {
-          path: ROUTE.home,
-          element: <Home />,
-          loader: checkAuth,
-        },
-        {
-          path: ROUTE.selectGroup,
-          element: <SelectGroup />,
-          loader: checkAuth,
-        },
-        {
-          path: ROUTE.groupSetup,
-          element: <GroupSetup />,
+          id: 'protected',
           loader: checkAuth,
+          element: <Outlet />,
+          children: [
+            {
+              path: ROUTE.onboarding,
+              element: <Onboarding />,
+            },
+            {
+              path: ROUTE.home,
+              element: <Home />,
+            },
+            {
+              path: ROUTE.selectGroup,
+              element: <SelectGroup />,
+            },
+            {
+              path: ROUTE.groupSetup,
+              element: <GroupSetup />,
+            },
+          ],
         },
+        // TODO : 로그인 기능으로 변경될 예정
         {
           path: ROUTE.createBill,
           element: <CreateBill />,
@@ -98,20 +105,15 @@ function AppRouter() {
           element: <CharacterShare />,
           loader: groupTokenUrlLoader,
         },
+        {
+          path: '*',
+          element: <NotFound />,
+        },
       ],
     },
-    {
-      path: '*',
-      element: <NotFound />,
-    },
   ]);
 
-  return (
-    // TODO : 로딩 페이지 추가하기
-    <Suspense fallback={<div>loading...</div>}>
-      <RouterProvider router={router} />
-    </Suspense>
-  );
+  return <RouterProvider router={router} />;
 }
 
 export default AppRouter;
diff --git a/src/entities/auth/api/auth.ts b/src/entities/auth/api/auth.ts
index a342663..e955802 100644
--- a/src/entities/auth/api/auth.ts
+++ b/src/entities/auth/api/auth.ts
@@ -1,5 +1,6 @@
 import axiosInstance from '@/shared/api/axios';
 
+// CHECK - 게스트 토큰 정책 제거 가능성 있음
 export interface GuestTokenData {
   accessToken: string;
   refreshToken: string;
@@ -11,3 +12,12 @@ export const getGuestToken = async (): Promise<GuestTokenData> => {
   const response = await axiosInstance.get('/user/guest/token');
   return response.data;
 };
+
+// ==========
+
+export const getAuth = async () => {
+  const response = await axiosInstance.get('/user/auth/check', {
+    useMock: true,
+  });
+  return response.data;
+};
diff --git a/src/entities/auth/lib/checkAuth.ts b/src/entities/auth/lib/checkAuth.ts
index fe55c3a..3f87391 100644
--- a/src/entities/auth/lib/checkAuth.ts
+++ b/src/entities/auth/lib/checkAuth.ts
@@ -1,21 +1,31 @@
 import { redirect } from 'react-router';
 import { ROUTE } from '@/shared/config/route';
+import { queryClient } from '@/shared/api/queryClient';
+import { getAuth } from '../api/auth';
 
 /**
  * 페이지에 접근하기 전에 실행되는 함수
- * -> accessToken이 있는지 확인하고, 없으면 login 으로 redirect
- *
- * @Todo accessToken 및 refreshToken 저장 방식 수정 후 로직 추가
- * 1. 메모리(전역상태변수로 관리)의 accessToken 존재 여부 확인
- * 2. 메모리에 accessToken이 없다면 httpOnly 쿠키를 확인 ->  refreshToken API 호출(refreshToken으로 accessToken 재발급)
- * 3. 쿠키에 refreshToken이 없다면 로그인 페이지로 redirect
  * */
-const checkAuth = () => {
-  const token = localStorage.getItem('accessToken');
-  if (!token) {
+const checkAuth = async () => {
+  try {
+    const user = await queryClient.ensureQueryData({
+      queryKey: ['auth', 'user'],
+      queryFn: getAuth,
+      staleTime: 5 * 60 * 1000, // 5 minutes
+      gcTime: 10 * 60 * 1000, // 10 minutes
+    });
+
+    if (!user || !user.authenticated) {
+      throw new Error('Unauthorized');
+    }
+
+    return user;
+  } catch {
+    // NOTE - 로그인 성공 후 이전 페이지로 돌아가기 위한 로직
+    // const redirectTo = new URL(request.url).pathname;
+    // return redirect(`${ROUTE.login}?redirectTo=${redirectTo}`);
     return redirect(ROUTE.login);
   }
-  return null;
 };
 
 export default checkAuth;
diff --git a/src/entities/auth/lib/kakaoLogin.ts b/src/entities/auth/lib/kakaoLogin.ts
new file mode 100644
index 0000000..668ad59
--- /dev/null
+++ b/src/entities/auth/lib/kakaoLogin.ts
@@ -0,0 +1,17 @@
+const KAKAO_CLIENT_ID = import.meta.env.VITE_KAKAO_CLIENT_ID;
+const KAKAO_REDIRECT_URI = import.meta.env.VITE_KAKAO_REDIRECT_URI;
+
+if (!KAKAO_CLIENT_ID || !KAKAO_REDIRECT_URI) {
+  throw new Error('카카오 OAuth에 필요한 환경 변수가 설정되지 않았습니다.');
+}
+
+function kakaoLogin(url?: string) {
+  const defaultRedirectUrl = window.location.origin;
+  const redirectUrl = url || defaultRedirectUrl;
+
+  window.location.href = `https://kauth.kakao.com/oauth/authorize?client_id=${KAKAO_CLIENT_ID}&redirect_uri=${KAKAO_REDIRECT_URI}&response_type=code&state=${encodeURIComponent(
+    redirectUrl
+  )}`;
+}
+
+export default kakaoLogin;
diff --git a/src/mocks/handlers/auth.ts b/src/mocks/handlers/auth.ts
index 1c085b5..f3af13a 100644
--- a/src/mocks/handlers/auth.ts
+++ b/src/mocks/handlers/auth.ts
@@ -11,6 +11,17 @@ const authHandlers = [
       isMember: false,
     });
   }),
+  http.get('/api/v1/user/auth/check', ({ request }) => {
+    const isMocked = request.headers.get('X-Mock-Request');
+    if (!isMocked || isMocked !== 'true') return passthrough();
+
+    console.log('유저 인증 체크 API 호출 - Mocked Response');
+
+    return HttpResponse.json({
+      authenticated: true,
+      user: { id: 'mock-test-user-id' },
+    });
+  }),
 ];
 
 export default authHandlers;
diff --git a/src/pages/login/LoginPage.tsx b/src/pages/login/LoginPage.tsx
index 1e4a9c9..4b90ad3 100644
--- a/src/pages/login/LoginPage.tsx
+++ b/src/pages/login/LoginPage.tsx
@@ -8,6 +8,7 @@ import Button from '@/shared/ui/Button';
 import { Kakao } from '@/shared/assets/svgs/icon';
 import Flex from '@/shared/ui/Flex';
 import { useGetGuestToken } from '@/entities/auth/api/useGetGuestToken';
+import kakaoLogin from '@/entities/auth/lib/kakaoLogin';
 import LoginEntranceView from './LoginEntranceView';
 import * as S from './LoginPage.styles';
 
@@ -19,7 +20,7 @@ function LoginPage() {
   const handleLoginButtonClick = (loginType: 'KAKAO' | 'GUEST') => {
     const token = localStorage.getItem('accessToken');
     if (loginType === 'KAKAO') {
-      console.log('카카오 로그인');
+      kakaoLogin();
     } else if (!token) {
       getGuestToken();
     } else {
@@ -60,7 +61,6 @@ function LoginPage() {
             background: '#FEE500',
           }}
           onClick={() => handleLoginButtonClick('KAKAO')}
-          disabled
         >
           <Kakao width={theme.unit[24]} />
           <Text variant="body1Sb" color="semantic.text.strong">
diff --git a/src/shared/api/queryClient.ts b/src/shared/api/queryClient.ts
new file mode 100644
index 0000000..dd030da
--- /dev/null
+++ b/src/shared/api/queryClient.ts
@@ -0,0 +1,19 @@
+import { QueryClient } from '@tanstack/react-query';
+
+export const queryClient = new QueryClient();
+
+export const setupQueryClient = (
+  handleQueryError: (error: Error) => void,
+  handleMutationError: (error: Error) => void
+) => {
+  queryClient.setDefaultOptions({
+    mutations: {
+      onError: handleMutationError,
+      throwOnError: true, // 기본적으로 RouteErrorBoundary로 에러를 던집니다.
+    },
+    queries: {
+      throwOnError: true, // 기본적으로 RouteErrorBoundary로 에러를 던집니다.
+    },
+  });
+  queryClient.getQueryCache().config.onError = handleQueryError;
+};