diff --git a/apps/web/src/app/styles.css b/apps/web/src/app/styles.css
index bd6a490..de52f4f 100644
--- a/apps/web/src/app/styles.css
+++ b/apps/web/src/app/styles.css
@@ -596,6 +596,80 @@ body {
   font-weight: 600;
 }
 
+.map-loader-overlay {
+  position: absolute;
+  inset: 0;
+  z-index: 950;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: rgba(2, 6, 23, 0.42);
+  pointer-events: auto;
+}
+
+.map-loader-overlay__panel {
+  width: min(72vw, 320px);
+  background: rgba(15, 23, 42, 0.94);
+  border: 1px solid var(--border);
+  border-radius: 12px;
+  padding: 14px 16px;
+  display: grid;
+  gap: 10px;
+  justify-items: center;
+}
+
+.map-loader-overlay__spinner {
+  width: 28px;
+  height: 28px;
+  border: 3px solid rgba(148, 163, 184, 0.28);
+  border-top-color: var(--accent);
+  border-radius: 50%;
+  animation: map-loader-spin 0.7s linear infinite;
+}
+
+.map-loader-overlay__text {
+  font-size: 12px;
+  color: var(--text);
+  letter-spacing: 0.2px;
+}
+
+.map-loader-overlay__bar {
+  width: 100%;
+  height: 6px;
+  border-radius: 999px;
+  background: rgba(148, 163, 184, 0.2);
+  overflow: hidden;
+  position: relative;
+}
+
+.map-loader-overlay__fill {
+  width: 28%;
+  height: 100%;
+  border-radius: inherit;
+  background: var(--accent);
+  animation: map-loader-fill 1.2s ease-in-out infinite;
+}
+
+@keyframes map-loader-spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
+@keyframes map-loader-fill {
+  0% {
+    transform: translateX(-40%);
+  }
+
+  50% {
+    transform: translateX(220%);
+  }
+
+  100% {
+    transform: translateX(-40%);
+  }
+}
+
 .close-btn {
   position: absolute;
   top: 6px;
diff --git a/apps/web/src/pages/dashboard/DashboardPage.tsx b/apps/web/src/pages/dashboard/DashboardPage.tsx
index ee949ac..c2f9453 100644
--- a/apps/web/src/pages/dashboard/DashboardPage.tsx
+++ b/apps/web/src/pages/dashboard/DashboardPage.tsx
@@ -115,6 +115,8 @@ export function DashboardPage() {
     showSeamark: false,
   });
 
+  const [isProjectionLoading, setIsProjectionLoading] = useState(false);
+
   const [clock, setClock] = useState(() => new Date().toLocaleString("ko-KR", { hour12: false }));
   useEffect(() => {
     const id = window.setInterval(() => setClock(new Date().toLocaleString("ko-KR", { hour12: false })), 1000);
@@ -472,6 +474,17 @@ export function DashboardPage() {
       </div>
 
       <div className="map-area">
+        {isProjectionLoading ? (
+          <div className="map-loader-overlay" role="status" aria-live="polite">
+            <div className="map-loader-overlay__panel">
+              <div className="map-loader-overlay__spinner" />
+              <div className="map-loader-overlay__text">지도 모드 동기화 중...</div>
+              <div className="map-loader-overlay__bar">
+                <div className="map-loader-overlay__fill" />
+              </div>
+            </div>
+          </div>
+        ) : null}
         <Map3D
           targets={targetsForMap}
           zones={zones}
@@ -486,6 +499,7 @@ export function DashboardPage() {
           pairLinks={pairLinksForMap}
           fcLinks={fcLinksForMap}
           fleetCircles={fleetCirclesForMap}
+          onProjectionLoadingChange={setIsProjectionLoading}
         />
         <MapLegend />
         {selectedLegacyVessel ? (
diff --git a/apps/web/src/widgets/map3d/Map3D.tsx b/apps/web/src/widgets/map3d/Map3D.tsx
index b5f7de9..241a0a7 100644
--- a/apps/web/src/widgets/map3d/Map3D.tsx
+++ b/apps/web/src/widgets/map3d/Map3D.tsx
@@ -42,6 +42,7 @@ type Props = {
   pairLinks?: PairLink[];
   fcLinks?: FcLink[];
   fleetCircles?: FleetCircle[];
+  onProjectionLoadingChange?: (loading: boolean) => void;
 };
 
 const SHIP_ICON_MAPPING = {
@@ -570,6 +571,7 @@ export function Map3D({
   pairLinks,
   fcLinks,
   fleetCircles,
+  onProjectionLoadingChange,
 }: Props) {
   const containerRef = useRef<HTMLDivElement | null>(null);
   const mapRef = useRef<maplibregl.Map | null>(null);
@@ -580,8 +582,41 @@ export function Map3D({
   const baseMapRef = useRef<BaseMapId>(baseMap);
   const projectionRef = useRef<MapProjectionId>(projection);
   const globeShipIconLoadingRef = useRef(false);
+  const projectionBusyRef = useRef(false);
+  const projectionBusyTimerRef = useRef<ReturnType<typeof window.setTimeout> | null>(null);
+  const projectionPrevRef = useRef<MapProjectionId>(projection);
   const [mapSyncEpoch, setMapSyncEpoch] = useState(0);
 
+  const clearProjectionBusyTimer = useCallback(() => {
+    if (projectionBusyTimerRef.current == null) return;
+    clearTimeout(projectionBusyTimerRef.current);
+    projectionBusyTimerRef.current = null;
+  }, []);
+
+  const setProjectionLoading = useCallback(
+    (loading: boolean) => {
+      if (projectionBusyRef.current === loading) return;
+      projectionBusyRef.current = loading;
+
+      if (loading) {
+        clearProjectionBusyTimer();
+        projectionBusyTimerRef.current = setTimeout(() => {
+          if (projectionBusyRef.current) {
+            setProjectionLoading(false);
+            console.warn("Projection loading fallback timeout reached.");
+          }
+        }, 18000);
+      } else {
+        clearProjectionBusyTimer();
+      }
+
+      if (onProjectionLoadingChange) {
+        onProjectionLoadingChange(loading);
+      }
+    },
+    [onProjectionLoadingChange, clearProjectionBusyTimer],
+  );
+
   const pulseMapSync = () => {
     setMapSyncEpoch((prev) => prev + 1);
     requestAnimationFrame(() => {
@@ -590,6 +625,15 @@ export function Map3D({
     });
   };
 
+  useEffect(() => {
+    return () => {
+      clearProjectionBusyTimer();
+      if (projectionBusyRef.current) {
+        setProjectionLoading(false);
+      }
+    };
+  }, [clearProjectionBusyTimer, setProjectionLoading]);
+
   useEffect(() => {
     showSeamarkRef.current = settings.showSeamark;
   }, [settings.showSeamark]);
@@ -816,6 +860,10 @@ export function Map3D({
     let cancelled = false;
     let retries = 0;
     const maxRetries = 18;
+    const isTransition = projectionPrevRef.current !== projection;
+    projectionPrevRef.current = projection;
+
+    if (isTransition) setProjectionLoading(true);
 
     const disposeMercatorOverlay = () => {
       const current = overlayRef.current;
@@ -852,6 +900,9 @@ export function Map3D({
 
     const syncProjectionAndDeck = () => {
       if (cancelled) return;
+      if (!isTransition) {
+        return;
+      }
 
       if (!map.isStyleLoaded()) {
         if (!cancelled && retries < maxRetries) {
@@ -889,6 +940,7 @@ export function Map3D({
           window.requestAnimationFrame(() => syncProjectionAndDeck());
           return;
         }
+        if (isTransition) setProjectionLoading(false);
         console.warn("Projection switch failed:", e);
       }
 
@@ -932,22 +984,39 @@ export function Map3D({
       } catch {
         // ignore
       }
+      if (isTransition) {
+        const mercatorReady = projection === "mercator" && !!overlayRef.current;
+        const globeReady = projection === "globe" && !!map.getLayer("deck-globe");
+        if (mercatorReady || globeReady) {
+          setProjectionLoading(false);
+        } else if (!cancelled && retries < maxRetries) {
+          retries += 1;
+          window.requestAnimationFrame(() => syncProjectionAndDeck());
+          return;
+        } else {
+          setProjectionLoading(false);
+        }
+      }
       pulseMapSync();
     };
 
+    if (!isTransition) return;
+
     if (map.isStyleLoaded()) syncProjectionAndDeck();
     else {
       const stop = onMapStyleReady(map, syncProjectionAndDeck);
       return () => {
         cancelled = true;
         stop();
+        if (isTransition) setProjectionLoading(false);
       };
     }
 
     return () => {
       cancelled = true;
+      if (isTransition) setProjectionLoading(false);
     };
-  }, [projection, clearGlobeNativeLayers, ensureMercatorOverlay, removeLayerIfExists]);
+  }, [projection, clearGlobeNativeLayers, ensureMercatorOverlay, removeLayerIfExists, setProjectionLoading]);
 
   // Base map toggle
   useEffect(() => {