diff --git a/frontend/src/app/fertilizer/_components/FertilizerEditPage.tsx b/frontend/src/app/fertilizer/_components/FertilizerEditPage.tsx
index 5f95e5a..1701ef9 100644
--- a/frontend/src/app/fertilizer/_components/FertilizerEditPage.tsx
+++ b/frontend/src/app/fertilizer/_components/FertilizerEditPage.tsx
@@ -143,7 +143,6 @@ export default function FertilizerEditPage({ planId }: { planId?: number }) {
   };
 
   const removeFertilizer = (id: number) => {
-    if (!confirm('この肥料を計画から削除しますか？')) return;
     setPlanFertilizers((prev) => prev.filter((f) => f.id !== id));
     setCalcSettings((prev) => prev.filter((s) => s.fertilizer_id !== id));
     const dropCol = (m: Matrix): Matrix => {
diff --git a/frontend/src/app/fertilizer/masters/page.tsx b/frontend/src/app/fertilizer/masters/page.tsx
index f8e5f78..6ba10b6 100644
--- a/frontend/src/app/fertilizer/masters/page.tsx
+++ b/frontend/src/app/fertilizer/masters/page.tsx
@@ -94,7 +94,6 @@ export default function FertilizerMastersPage() {
   };
 
   const handleDelete = async (id: number, name: string) => {
-    if (!confirm(`「${name}」を削除しますか？`)) return;
     setDeleteError(null);
     try {
       await api.delete(`/fertilizer/fertilizers/${id}/`);
diff --git a/frontend/src/app/fertilizer/page.tsx b/frontend/src/app/fertilizer/page.tsx
index 7e98a63..14a4082 100644
--- a/frontend/src/app/fertilizer/page.tsx
+++ b/frontend/src/app/fertilizer/page.tsx
@@ -20,6 +20,7 @@ export default function FertilizerPage() {
   });
   const [plans, setPlans] = useState<FertilizationPlan[]>([]);
   const [loading, setLoading] = useState(true);
+  const [deleteError, setDeleteError] = useState<string | null>(null);
 
   useEffect(() => {
     localStorage.setItem('fertilizerYear', String(year));
@@ -39,13 +40,13 @@ export default function FertilizerPage() {
   };
 
   const handleDelete = async (id: number, name: string) => {
-    if (!confirm(`「${name}」を削除しますか？`)) return;
+    setDeleteError(null);
     try {
       await api.delete(`/fertilizer/plans/${id}/`);
       await fetchPlans();
     } catch (e) {
       console.error(e);
-      alert('削除に失敗しました');
+      setDeleteError(`「${name}」の削除に失敗しました`);
     }
   };
 
@@ -106,6 +107,14 @@ export default function FertilizerPage() {
           </select>
         </div>
 
+        {deleteError && (
+          <div className="mb-4 flex items-start gap-2 bg-red-50 border border-red-300 text-red-700 rounded-lg px-4 py-3 text-sm">
+            <span className="font-bold shrink-0">⚠</span>
+            <span>{deleteError}</span>
+            <button onClick={() => setDeleteError(null)} className="ml-auto shrink-0 text-red-400 hover:text-red-600">✕</button>
+          </div>
+        )}
+
         {loading ? (
           <p className="text-gray-500">読み込み中...</p>
         ) : plans.length === 0 ? (