diff --git a/README.md b/README.md
index 76940b20171..791453c64be 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,7 @@ Works with any CLI agent. Built for local worktree-based development.
 | **大規模ファイル diff 高速化** | 2000行超のファイルで CodeMirror 6 ベースの仮想化 diff ビューアに自動切替。ビューポート分のDOMのみ描画し、15000行でもスムーズ表示。既存テーマ・シンタックスハイライト再利用、未変更領域の自動折りたたみ | [#5](https://github.com/MocA-Love/superset/pull/5) | 2026-03-28 |
 | **ports.json ポートの常時表示** | ports.json に定義されたポートをプロセス検出の有無にかかわらず常にサイドバーに表示。Docker 等で検知できないポートもラベル付きで一覧に出る。検出済みポートは従来通りアクティブ表示、未検出は グレー表示で区別 | [#7](https://github.com/MocA-Love/superset/pull/7) | 2026-03-28 |
 | **Ports ワークスペース名の改善** | Ports セクションのワークスペース名をワークツリーのディレクトリ名ベースに変更。同名ワークスペースが複数ある場合でもどのワークツリーか一目で区別可能 | [#8](https://github.com/MocA-Love/superset/pull/8) | 2026-03-28 |
+| **ブラウザタブのズーム機能** | ブラウザタブのツールバーに拡大（+）・縮小（-）・リセットボタンを追加。webview の zoom API を直接操作し、50%〜200% の範囲でズーム可能。パーセント表示クリックで 100% にリセット | [#9](https://github.com/MocA-Love/superset/pull/9) | 2026-03-29 |
 
 ## Fork のビルド方法 (macOS)
 
diff --git a/apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/TabView/BrowserPane/BrowserPane.tsx b/apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/TabView/BrowserPane/BrowserPane.tsx
index 0225544e8bb..e3774ba78cd 100644
--- a/apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/TabView/BrowserPane/BrowserPane.tsx
+++ b/apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/TabView/BrowserPane/BrowserPane.tsx
@@ -1,6 +1,7 @@
 import { Tooltip, TooltipContent, TooltipTrigger } from "@superset/ui/tooltip";
 import { GlobeIcon } from "lucide-react";
-import { useCallback } from "react";
+import { useCallback, useState } from "react";
+import { LuMinus, LuPlus } from "react-icons/lu";
 import { TbDeviceDesktop } from "react-icons/tb";
 import type { MosaicBranch } from "react-mosaic-component";
 import { electronTrpc } from "renderer/lib/electron-trpc";
@@ -53,11 +54,38 @@ export function BrowserPane({
 		navigateTo,
 		canGoBack,
 		canGoForward,
+		setGuestZoom,
 	} = usePersistentWebview({
 		paneId,
 		initialUrl: currentUrl,
 	});
 
+	// -- Zoom state (CSS zoom injected into guest page) ---------------------
+
+	const ZOOM_STEP = 10;
+	const ZOOM_MIN = 50;
+	const ZOOM_MAX = 200;
+
+	const [zoomPercent, setZoomPercent] = useState(100);
+
+	const applyZoom = useCallback(
+		(percent: number) => {
+			setZoomPercent(percent);
+			setGuestZoom(percent / 100);
+		},
+		[setGuestZoom],
+	);
+
+	const zoomIn = useCallback(
+		() => applyZoom(Math.min(ZOOM_MAX, zoomPercent + ZOOM_STEP)),
+		[applyZoom, zoomPercent],
+	);
+	const zoomOut = useCallback(
+		() => applyZoom(Math.max(ZOOM_MIN, zoomPercent - ZOOM_STEP)),
+		[applyZoom, zoomPercent],
+	);
+	const resetZoom = useCallback(() => applyZoom(100), [applyZoom]);
+
 	const handleOpenDevTools = useCallback(() => {
 		openDevTools({ paneId });
 	}, [openDevTools, paneId]);
@@ -92,6 +120,50 @@ export function BrowserPane({
 							closeHotkeyId="CLOSE_TERMINAL"
 							leadingActions={
 								<>
+									<div className="flex items-center gap-0.5">
+										<Tooltip>
+											<TooltipTrigger asChild>
+												<button
+													type="button"
+													onClick={zoomOut}
+													className="rounded p-0.5 text-muted-foreground/60 transition-colors hover:text-muted-foreground"
+												>
+													<LuMinus className="size-3.5" />
+												</button>
+											</TooltipTrigger>
+											<TooltipContent side="bottom" showArrow={false}>
+												Zoom Out
+											</TooltipContent>
+										</Tooltip>
+										<Tooltip>
+											<TooltipTrigger asChild>
+												<button
+													type="button"
+													onClick={resetZoom}
+													className="rounded px-1 py-0.5 text-[10px] tabular-nums text-muted-foreground/60 transition-colors hover:text-muted-foreground"
+												>
+													{zoomPercent}%
+												</button>
+											</TooltipTrigger>
+											<TooltipContent side="bottom" showArrow={false}>
+												Reset Zoom
+											</TooltipContent>
+										</Tooltip>
+										<Tooltip>
+											<TooltipTrigger asChild>
+												<button
+													type="button"
+													onClick={zoomIn}
+													className="rounded p-0.5 text-muted-foreground/60 transition-colors hover:text-muted-foreground"
+												>
+													<LuPlus className="size-3.5" />
+												</button>
+											</TooltipTrigger>
+											<TooltipContent side="bottom" showArrow={false}>
+												Zoom In
+											</TooltipContent>
+										</Tooltip>
+									</div>
 									<Tooltip>
 										<TooltipTrigger asChild>
 											<button
diff --git a/apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/TabView/BrowserPane/hooks/usePersistentWebview/usePersistentWebview.ts b/apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/TabView/BrowserPane/hooks/usePersistentWebview/usePersistentWebview.ts
index 1412808a396..3921f06c7a6 100644
--- a/apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/TabView/BrowserPane/hooks/usePersistentWebview/usePersistentWebview.ts
+++ b/apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/TabView/BrowserPane/hooks/usePersistentWebview/usePersistentWebview.ts
@@ -24,6 +24,8 @@ const webviewRegistry = new Map<string, Electron.WebviewTag>();
 const wrapperRegistry = new Map<string, HTMLDivElement>();
 /** Tracks paneId → last-registered webContentsId so we can re-register if it changes. */
 const registeredWebContentsIds = new Map<string, number>();
+/** Tracks paneId → current CSS zoom factor so it can be re-applied after page loads. */
+const zoomFactorRegistry = new Map<string, number>();
 let hiddenContainer: HTMLDivElement | null = null;
 
 function getHiddenContainer(): HTMLDivElement {
@@ -84,6 +86,7 @@ export function destroyPersistentWebview(paneId: string): void {
 		webviewRegistry.delete(paneId);
 	}
 	registeredWebContentsIds.delete(paneId);
+	zoomFactorRegistry.delete(paneId);
 }
 
 // ---------------------------------------------------------------------------
@@ -275,24 +278,31 @@ export function usePersistentWebview({
 
 			if (isHistoryNavigation.current) {
 				isHistoryNavigation.current = false;
-				return;
+			} else {
+				const url = wv.getURL();
+				const title = wv.getTitle();
+				store.updateBrowserUrl(
+					paneId,
+					url ?? "",
+					title ?? "",
+					faviconUrlRef.current,
+				);
+
+				if (url && url !== "about:blank") {
+					upsertHistory({
+						url,
+						title: title ?? "",
+						faviconUrl: faviconUrlRef.current ?? null,
+					});
+				}
 			}
 
-			const url = wv.getURL();
-			const title = wv.getTitle();
-			store.updateBrowserUrl(
-				paneId,
-				url ?? "",
-				title ?? "",
-				faviconUrlRef.current,
-			);
-
-			if (url && url !== "about:blank") {
-				upsertHistory({
-					url,
-					title: title ?? "",
-					faviconUrl: faviconUrlRef.current ?? null,
-				});
+			// Re-apply CSS zoom after page load (zoom is lost on navigation/reload)
+			const factor = zoomFactorRegistry.get(paneId);
+			if (factor != null && factor !== 1) {
+				wv.executeJavaScript(
+					`document.documentElement.style.zoom = '${factor}'`,
+				).catch(() => {});
 			}
 		};
 
@@ -459,6 +469,23 @@ export function usePersistentWebview({
 		[paneId],
 	);
 
+	// -- Zoom (CSS zoom injected into guest page — guaranteed host-safe) ----
+
+	const setGuestZoom = useCallback(
+		(factor: number) => {
+			zoomFactorRegistry.set(paneId, factor);
+			const webview = webviewRegistry.get(paneId);
+			if (webview) {
+				webview
+					.executeJavaScript(
+						`document.documentElement.style.zoom = '${factor}'`,
+					)
+					.catch(() => {});
+			}
+		},
+		[paneId],
+	);
+
 	return {
 		containerRef,
 		goBack,
@@ -467,5 +494,6 @@ export function usePersistentWebview({
 		navigateTo,
 		canGoBack,
 		canGoForward,
+		setGuestZoom,
 	};
 }