diff --git a/index.html b/index.html
index dc3d047..d8305ca 100644
--- a/index.html
+++ b/index.html
@@ -422,7 +422,7 @@ header{display:flex;align-items:center;justify-content:space-between;padding:0 1
       <!-- UNIT VIEW -->
       <div x-show="currentUnit">
         <div class="unit-header">
-          <button class="unit-back" @click="currentUnit=null;quizState={}">
+          <button class="unit-back" @click="goHome()">
             <i data-lucide="arrow-left" style="width:12px;height:12px"></i>
             一覧
           </button>
@@ -790,12 +790,38 @@ function bokiApp(){
       catch{ this.scores = {}; }
       const t = localStorage.getItem('posimai-boki-theme')||'system';
       this.isDark = t==='dark'||(t==='system'&&matchMedia('(prefers-color-scheme:dark)').matches);
+      const uid=(new URLSearchParams(location.search).get('unit')||'').trim().toLowerCase();
+      if(uid){
+        const u=this.allUnits().find(x=>x.id===uid);
+        if(u){ this.currentUnit=u; this.quizState={}; }
+        else{ try{ const url=new URL(window.location.href); url.searchParams.delete('unit'); const q=url.searchParams.toString(); history.replaceState(null,'',url.pathname+(q?'?'+q:'')+url.hash); }catch(e){} }
+      }
+      this.syncUnitToUrl();
       this.$nextTick(()=>{ if(window.lucide) lucide.createIcons(); });
       if('serviceWorker' in navigator){
         navigator.serviceWorker.register('/sw.js').catch(()=>{});
       }
     },
 
+    syncUnitToUrl(){
+      try{
+        const url=new URL(window.location.href);
+        if(this.currentUnit&&this.currentUnit.id) url.searchParams.set('unit',this.currentUnit.id);
+        else url.searchParams.delete('unit');
+        const q=url.searchParams.toString();
+        const path=url.pathname+(q?'?'+q:'')+url.hash;
+        if(path!==window.location.pathname+window.location.search+window.location.hash)
+          history.replaceState(null,'',path);
+      }catch(e){}
+    },
+
+    goHome(){
+      this.currentUnit=null;
+      this.quizState={};
+      this.syncUnitToUrl();
+      this.$nextTick(()=>{ if(window.lucide) lucide.createIcons(); });
+    },
+
     get filteredCats(){
       if(!this.search) return this.categories;
       const q=this.search.toLowerCase();
@@ -872,6 +898,7 @@ function bokiApp(){
     openUnit(unit){
       this.currentUnit=unit;
       this.quizState={};
+      this.syncUnitToUrl();
       this.$nextTick(()=>{
         if(window.lucide) lucide.createIcons();
         const m=document.getElementById('main');
diff --git a/sw.js b/sw.js
index b45a0e0..64e558c 100644
--- a/sw.js
+++ b/sw.js
@@ -1,5 +1,5 @@
 // posimai-boki SW — stale-while-revalidate + skipWaiting
-const CACHE = 'posimai-boki-v9';
+const CACHE = 'posimai-boki-v10';
 const STATIC = ['/', '/index.html', '/manifest.json', '/logo.png'];
 
 self.addEventListener('install', e => {