diff --git a/app/Http/Controllers/Api/CardController.php b/app/Http/Controllers/Api/CardController.php
index a336830..aeaa37a 100644
--- a/app/Http/Controllers/Api/CardController.php
+++ b/app/Http/Controllers/Api/CardController.php
@@ -44,7 +44,7 @@ class CardController
             ]);
 
             $tagIds = [];
-            foreach ($resolved->tags as $tagName) {
+            foreach ($resolved->normalizedTags() as $tagName) {
                 $tag = Tag::firstOrCreate(['name' => $tagName]);
                 $tagIds[] = $tag->id;
             }
diff --git a/app/Listeners/LinkCollector.php b/app/Listeners/LinkCollector.php
index 1ca8682..867938f 100644
--- a/app/Listeners/LinkCollector.php
+++ b/app/Listeners/LinkCollector.php
@@ -56,7 +56,7 @@ class LinkCollector
                 ]);
 
                 $tagIds = [];
-                foreach ($resolved->tags as $tagName) {
+                foreach ($resolved->normalizedTags() as $tagName) {
                     $tag = Tag::firstOrCreate(['name' => $tagName]);
                     $tagIds[] = $tag->id;
                 }
diff --git a/app/MetadataResolver/Metadata.php b/app/MetadataResolver/Metadata.php
index 62d16e8..c9b5e05 100644
--- a/app/MetadataResolver/Metadata.php
+++ b/app/MetadataResolver/Metadata.php
@@ -23,4 +23,30 @@ class Metadata
      * チェックインタグと同様に保存されるため、スペースや改行文字を含めてはいけません。
      */
     public $tags = [];
+
+    /**
+     * 重複を排除し、正規化を行ったタグの集合を返します。
+     * @return string[]
+     */
+    public function normalizedTags(): array
+    {
+        $tags = [];
+        foreach ($this->tags as $tag) {
+            $tag = $this->sanitize($tag);
+            $tag = $this->trim($tag);
+            $tags[$tag] = true;
+        }
+
+        return array_keys($tags);
+    }
+
+    private function sanitize(string $value): string
+    {
+        return preg_replace('/\r?\n/u', ' ', $value);
+    }
+
+    private function trim(string $value): string
+    {
+        return trim($value);
+    }
 }
diff --git a/tests/Unit/MetadataResolver/MetadataTest.php b/tests/Unit/MetadataResolver/MetadataTest.php
new file mode 100644
index 0000000..6d517ac
--- /dev/null
+++ b/tests/Unit/MetadataResolver/MetadataTest.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace Tests\Unit\MetadataResolver;
+
+use App\MetadataResolver\Metadata;
+use Tests\TestCase;
+
+class MetadataTest extends TestCase
+{
+    public function testNormalizedTagsCanTrim()
+    {
+        $metadata = new Metadata();
+        $metadata->tags = ['foo ', ' bar', ' foo bar '];
+
+        $this->assertEquals(['foo', 'bar', 'foo bar'], $metadata->normalizedTags());
+    }
+
+    public function testNormalizedTagsCanSanitize()
+    {
+        $metadata = new Metadata();
+        $metadata->tags = ["foo \n", " \nbar", " foo\n bar "];
+
+        $this->assertEquals(['foo', 'bar', 'foo  bar'], $metadata->normalizedTags());
+    }
+
+    public function testNormalizedTagsCanDeduplication()
+    {
+        $metadata = new Metadata();
+        $metadata->tags = ['foo ', ' foo', ' bar'];
+
+        $this->assertEquals(['foo', 'bar'], $metadata->normalizedTags());
+    }
+}