diff --git a/client/src/features/CasperCustom/CasperCustomFinish.tsx b/client/src/features/CasperCustom/CasperCustomFinish.tsx
index 54c4e1ed..4e0b8914 100644
--- a/client/src/features/CasperCustom/CasperCustomFinish.tsx
+++ b/client/src/features/CasperCustom/CasperCustomFinish.tsx
@@ -21,9 +21,13 @@ import ArrowIcon from "/public/assets/icons/arrow.svg?react";
 
 interface CasperCustomFinishProps {
     handleResetStep: () => void;
+    unblockNavigation: () => void;
 }
 
-export function CasperCustomFinish({ handleResetStep }: CasperCustomFinishProps) {
+export function CasperCustomFinish({
+    handleResetStep,
+    unblockNavigation,
+}: CasperCustomFinishProps) {
     const [cookies] = useCookies([COOKIE_TOKEN_KEY]);
 
     const {
@@ -41,6 +45,8 @@ export function CasperCustomFinish({ handleResetStep }: CasperCustomFinishProps)
         if (!cookies[COOKIE_TOKEN_KEY]) {
             return;
         }
+
+        unblockNavigation();
         getApplyCount();
     }, [cookies]);
 
diff --git a/client/src/features/CasperCustom/CasperCustomFinishing.tsx b/client/src/features/CasperCustom/CasperCustomFinishing.tsx
index e99b4681..a5befcba 100644
--- a/client/src/features/CasperCustom/CasperCustomFinishing.tsx
+++ b/client/src/features/CasperCustom/CasperCustomFinishing.tsx
@@ -27,13 +27,18 @@ export function CasperCustomFinishing({ navigateNextStep }: CasperCustomFinishin
     useEffect(() => {
         showToast();
 
-        setTimeout(() => {
+        const flipTimer = setTimeout(() => {
             setIsFlipped(true);
         }, 3000);
 
-        setTimeout(() => {
+        const navigateTimer = setTimeout(() => {
             navigateNextStep();
         }, 6000);
+
+        return () => {
+            clearTimeout(flipTimer);
+            clearTimeout(navigateTimer);
+        };
     }, []);
 
     return (
diff --git a/client/src/hooks/useBlockNavigation.ts b/client/src/hooks/useBlockNavigation.ts
new file mode 100644
index 00000000..e43d4c0c
--- /dev/null
+++ b/client/src/hooks/useBlockNavigation.ts
@@ -0,0 +1,37 @@
+import { useEffect, useState } from "react";
+import { unstable_usePrompt, useLocation } from "react-router-dom";
+
+export function useBlockNavigation(message: string) {
+    const location = useLocation();
+    const [isBlocking, setIsBlocking] = useState(false);
+
+    unstable_usePrompt({ when: isBlocking, message });
+
+    const unblockNavigation = () => {
+        setIsBlocking(false);
+    };
+
+    const handleBeforeUnload = (e: BeforeUnloadEvent) => {
+        if (isBlocking) {
+            e.preventDefault();
+            e.returnValue = "";
+        }
+    };
+
+    useEffect(() => {
+        setIsBlocking(true);
+
+        return () => {
+            setIsBlocking(false);
+        };
+    }, [location]);
+    useEffect(() => {
+        window.addEventListener("beforeunload", handleBeforeUnload);
+
+        return () => {
+            window.removeEventListener("beforeunload", handleBeforeUnload);
+        };
+    }, [isBlocking]);
+
+    return { unblockNavigation };
+}
diff --git a/client/src/pages/CasperCustom/index.tsx b/client/src/pages/CasperCustom/index.tsx
index 91655af9..6155e1d9 100644
--- a/client/src/pages/CasperCustom/index.tsx
+++ b/client/src/pages/CasperCustom/index.tsx
@@ -14,12 +14,17 @@ import {
     CasperCustomForm,
     CasperCustomProcess,
 } from "@/features/CasperCustom";
+import { useBlockNavigation } from "@/hooks/useBlockNavigation";
 import useHeaderStyleObserver from "@/hooks/useHeaderStyleObserver";
 import { SCROLL_MOTION } from "../../constants/animation";
 
 const INITIAL_STEP = 0;
 
 export default function CasperCustom() {
+    const { unblockNavigation } = useBlockNavigation(
+        "이 페이지를 떠나면 모든 변경 사항이 저장되지 않습니다. 페이지를 떠나시겠습니까?"
+    );
+
     const containerRef = useHeaderStyleObserver({
         darkSections: [CASPER_CUSTOM_SECTIONS.CUSTOM],
     });
@@ -28,7 +33,7 @@ export default function CasperCustom() {
     const selectedStep = CUSTOM_STEP_OPTION_ARRAY[selectedStepIdx];
 
     const handleClickNextStep = () => {
-        setSelectedStepIdx(selectedStepIdx + 1);
+        setSelectedStepIdx((prevSelectedIdx) => prevSelectedIdx + 1);
     };
 
     const handleResetStep = () => {
@@ -43,7 +48,12 @@ export default function CasperCustom() {
         } else if (selectedStep === CUSTOM_STEP_OPTION.FINISHING) {
             return <CasperCustomFinishing navigateNextStep={handleClickNextStep} />;
         } else if (selectedStep === CUSTOM_STEP_OPTION.FINISH) {
-            return <CasperCustomFinish handleResetStep={handleResetStep} />;
+            return (
+                <CasperCustomFinish
+                    handleResetStep={handleResetStep}
+                    unblockNavigation={unblockNavigation}
+                />
+            );
         }
         return <></>;
     };
diff --git a/client/src/types/lotteryApi.ts b/client/src/types/lotteryApi.ts
index 3b7d9c40..55b5253d 100644
--- a/client/src/types/lotteryApi.ts
+++ b/client/src/types/lotteryApi.ts
@@ -24,8 +24,7 @@ export interface GetApplyCountResponse {
 }
 
 export interface GetLotteryResponse {
-    lotteryEventId: number;
     eventStartDate: string;
     eventEndDate: string;
-    winnerCount: number;
+    activePeriod: number;
 }