diff --git a/TIASshot.Tests/IoUtilWriteInfoTests.cs b/TIASshot.Tests/IoUtilWriteInfoTests.cs
new file mode 100644
index 0000000..dff11c1
--- /dev/null
+++ b/TIASshot.Tests/IoUtilWriteInfoTests.cs
@@ -0,0 +1,92 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using NUnit.Framework;
+
+namespace TIASshot.Tests {
+    /// <summary>
+    /// IoUtil.WriteInfo（撮影情報 Info.csv の書き出し）のテスト．
+    /// 値にカンマ・ダブルクォート・改行が含まれても 1 項目が 1 行（キー,値 の 2 列）に保たれ，
+    /// RFC 4180 に従ってクォートされることを検証する．それ以外の値は従来どおりそのまま出力する．
+    /// </summary>
+    [TestFixture]
+    public class IoUtilWriteInfoTests {
+
+        private string _csvPath;
+
+        [SetUp]
+        public void SetUp() {
+            _csvPath = Path.GetTempFileName();
+        }
+
+        [TearDown]
+        public void TearDown() {
+            if (File.Exists(_csvPath)) File.Delete(_csvPath);
+        }
+
+        /// <summary>
+        /// 本番（RunShotLoop）と同じく new StreamWriter(path) で WriteInfo を呼び，
+        /// 先頭の撮影日時行を除いた本文を返す
+        /// </summary>
+        private string WriteAndReadBody(Dictionary<string, string> info) {
+            using (var sw = new StreamWriter(_csvPath)) {
+                IoUtil.WriteInfo(sw, info);
+            }
+            var text = File.ReadAllText(_csvPath, Encoding.UTF8);
+            var firstNewLine = text.IndexOf("\r\n");
+            return text.Substring(firstNewLine + 2);
+        }
+
+        [Test]
+        public void WriteInfo_特殊文字を含まない値_従来どおりそのまま出力する() {
+            var info = new Dictionary<string, string> {
+                { "データ名", "subject01" },
+                { "Exposure(ms)", "12.5" },
+                { "校正データ", @"C:\Data\2026-10-06\10_00_00-校正" },
+            };
+
+            var body = WriteAndReadBody(info);
+
+            Assert.That(body, Is.EqualTo(
+                "データ名,subject01\r\n" +
+                "Exposure(ms),12.5\r\n" +
+                "校正データ,C:\\Data\\2026-10-06\\10_00_00-校正\r\n"));
+        }
+
+        [Test]
+        public void WriteInfo_値にカンマを含む_ダブルクォートで囲む() {
+            var info = new Dictionary<string, string> { { "データ名", "山田,太郎" } };
+
+            var body = WriteAndReadBody(info);
+
+            Assert.That(body, Is.EqualTo("データ名,\"山田,太郎\"\r\n"));
+        }
+
+        [Test]
+        public void WriteInfo_値にダブルクォートを含む_二重化してダブルクォートで囲む() {
+            var info = new Dictionary<string, string> { { "データ名", "a\"b" } };
+
+            var body = WriteAndReadBody(info);
+
+            Assert.That(body, Is.EqualTo("データ名,\"a\"\"b\"\r\n"));
+        }
+
+        [Test]
+        public void WriteInfo_値に改行を含む_ダブルクォートで囲み1レコードに保つ() {
+            var info = new Dictionary<string, string> { { "データ名", "a\r\nb" } };
+
+            var body = WriteAndReadBody(info);
+
+            Assert.That(body, Is.EqualTo("データ名,\"a\r\nb\"\r\n"));
+        }
+
+        [Test]
+        public void WriteInfo_値がnull_空欄として出力する() {
+            var info = new Dictionary<string, string> { { "データ名", null } };
+
+            var body = WriteAndReadBody(info);
+
+            Assert.That(body, Is.EqualTo("データ名,\r\n"));
+        }
+    }
+}
diff --git a/TIASshot.Tests/TIASshot.Tests.csproj b/TIASshot.Tests/TIASshot.Tests.csproj
index 2ab809f..504bc4a 100644
--- a/TIASshot.Tests/TIASshot.Tests.csproj
+++ b/TIASshot.Tests/TIASshot.Tests.csproj
@@ -93,6 +93,7 @@
     <Compile Include="IoUtilCreateSaveFolderTests.cs" />
     <Compile Include="IoUtilCombineSaveFilePathTests.cs" />
     <Compile Include="IoUtilSaveImageTests.cs" />
+    <Compile Include="IoUtilWriteInfoTests.cs" />
     <Compile Include="ConfigTests.cs" />
     <Compile Include="ColorCorrectorTests.cs" />
     <Compile Include="ChartDetectorTests.cs" />