diff --git a/CHANGELOG.md b/CHANGELOG.md
index 360b52e..6362b93 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Changed
+
+- Allow to change the target of observer ([#28](https://github.com/marp-team/marpit-svg-polyfill/pull/28))
+
 ## v1.5.0 - 2020-07-16
 
 ### Changed
diff --git a/src/entry.ts b/src/entry.ts
index 52134eb..6ea3d8b 100644
--- a/src/entry.ts
+++ b/src/entry.ts
@@ -1,2 +1,8 @@
 /* istanbul ignore file */
-export { observe as default, observe, polyfills, webkit } from './polyfill'
+export {
+  PolyfillOption,
+  observe as default,
+  observe,
+  polyfills,
+  webkit,
+} from './polyfill'
diff --git a/src/polyfill.ts b/src/polyfill.ts
index 7b570d8..5d6fecf 100644
--- a/src/polyfill.ts
+++ b/src/polyfill.ts
@@ -1,28 +1,39 @@
 const msgPrefix = 'marpitSVGPolyfill:setZoomFactor,'
 
+export type PolyfillOption = { target?: ParentNode }
+
 export const observerSymbol = Symbol()
 export const zoomFactorRecieverSymbol = Symbol()
 
-export function observe() {
-  if (window[observerSymbol]) return
+export function observe(target: ParentNode = document): () => void {
+  if (target[observerSymbol]) return target[observerSymbol]
+
+  let enableObserver = true
+
+  const cleanup = () => {
+    enableObserver = false
+    delete target[observerSymbol]
+  }
 
-  Object.defineProperty(window, observerSymbol, {
+  Object.defineProperty(target, observerSymbol, {
     configurable: true,
-    value: true,
+    value: cleanup,
   })
 
   const observedPolyfills = polyfills()
 
   if (observedPolyfills.length > 0) {
     const observer = () => {
-      for (const polyfill of observedPolyfills) polyfill()
-      window.requestAnimationFrame(observer)
+      for (const polyfill of observedPolyfills) polyfill({ target })
+      if (enableObserver) window.requestAnimationFrame(observer)
     }
     observer()
   }
+
+  return cleanup
 }
 
-export const polyfills = () =>
+export const polyfills = (): Array<(opts: PolyfillOption) => void> =>
   navigator.vendor === 'Apple Computer, Inc.' ? [webkit] : []
 
 let previousZoomFactor: number
@@ -35,7 +46,10 @@ export const _resetCachedZoomFactor = () => {
 
 _resetCachedZoomFactor()
 
-export function webkit(zoom?: number) {
+export function webkit(opts?: number | (PolyfillOption & { zoom?: number })) {
+  const target = (typeof opts === 'object' && opts.target) || document
+  const zoom = typeof opts === 'object' ? opts.zoom : opts
+
   if (!window[zoomFactorRecieverSymbol]) {
     Object.defineProperty(window, zoomFactorRecieverSymbol, {
       configurable: true,
@@ -61,7 +75,7 @@ export function webkit(zoom?: number) {
   let changedZoomFactor: false | number = false
 
   Array.from(
-    document.querySelectorAll<SVGSVGElement>('svg[data-marpit-svg]'),
+    target.querySelectorAll<SVGSVGElement>('svg[data-marpit-svg]'),
     (svg) => {
       const { children, clientHeight, clientWidth, viewBox } = svg
       if (!svg.style.transform) svg.style.transform = 'translateZ(0)'
@@ -93,7 +107,7 @@ export function webkit(zoom?: number) {
 
   if (changedZoomFactor !== false) {
     Array.from(
-      document.querySelectorAll<HTMLIFrameElement>('iframe'),
+      target.querySelectorAll<HTMLIFrameElement>('iframe'),
       ({ contentWindow }) => {
         contentWindow?.postMessage(
           `${msgPrefix}${changedZoomFactor}`,
diff --git a/test/polyfill.ts b/test/polyfill.ts
index 6299dfc..68f9696 100644
--- a/test/polyfill.ts
+++ b/test/polyfill.ts
@@ -9,7 +9,7 @@ import {
 let vendor: jest.SpyInstance
 
 beforeEach(() => {
-  window[observerSymbol] = false
+  delete document[observerSymbol]
   vendor = jest.spyOn(navigator, 'vendor', 'get').mockImplementation(() => '')
   _resetCachedZoomFactor()
 })
@@ -37,6 +37,37 @@ describe('Marpit SVG polyfill', () => {
       observe()
       expect(spy).toHaveBeenCalledTimes(1)
     })
+
+    describe('Clean-up function', () => {
+      it('returns function for clean-up', () => {
+        vendor.mockImplementation(() => 'Apple Computer, Inc.')
+
+        const cleanup = observe()
+        expect(cleanup).toStrictEqual(expect.any(Function))
+
+        // Observer can enable again after cleaning up
+        cleanup()
+        observe()
+        expect(spy).toHaveBeenCalledTimes(2)
+      })
+    })
+
+    describe('Different target', () => {
+      it('availables observation for different target', () => {
+        vendor.mockImplementation(() => 'Apple Computer, Inc.')
+
+        const element = document.createElement('div')
+        const querySpy = jest.spyOn(element, 'querySelectorAll')
+        const cleanup = observe(element)
+
+        expect(element[observerSymbol]).toStrictEqual(cleanup)
+        expect(querySpy).toHaveBeenCalled()
+
+        // Returns always same clean-up function even if observing some times
+        expect(observe(element)).toStrictEqual(cleanup)
+        expect(spy).toHaveBeenCalledTimes(1)
+      })
+    })
   })
 
   describe('#webkit', () => {