diff --git a/Runtime/Attributes/TakeScreenshotAttribute.cs b/Runtime/Attributes/TakeScreenshotAttribute.cs
index 7dae741..9548023 100644
--- a/Runtime/Attributes/TakeScreenshotAttribute.cs
+++ b/Runtime/Attributes/TakeScreenshotAttribute.cs
@@ -1,4 +1,4 @@
-// Copyright (c) 2023 Koji Hasegawa.
+// Copyright (c) 2023-2024 Koji Hasegawa.
 // This software is released under the MIT License.
 
 using System;
@@ -26,7 +26,7 @@ public class TakeScreenshotAttribute : NUnitAttribute, IOuterUnityTestAction
         /// <summary>
         /// Take a screenshot and save it to file after running the test.
         /// Default save path is $"{Application.persistentDataPath}/TestHelper/Screenshots/{CurrentTest.Name}.png".
-        /// If you want to take screenshots at any time, use the <c>ScreenshotHelper</c> class.
+        /// If you want to take screenshots at any time, use the <c>TestHelper.RuntimeInternals.ScreenshotHelper</c> class.
         /// </summary>
         /// <remarks>
         /// Limitations:
@@ -35,8 +35,12 @@ public class TakeScreenshotAttribute : NUnitAttribute, IOuterUnityTestAction
         /// <br/>
         /// Using <c>ScreenCapture.CaptureScreenshotAsTexture</c> internally.
         /// </remarks>
-        /// <param name="directory">Directory to save screenshots.</param>
-        /// <param name="filename">Filename to store screenshot.</param>
+        /// <param name="directory">Directory to save screenshots.
+        /// If omitted, the directory specified by command line argument "-testHelperScreenshotDirectory" is used.
+        /// If the command line argument is also omitted, <c>Application.persistentDataPath</c> + "/TestHelper/Screenshots/" is used.</param>
+        /// <param name="filename">Filename to store screenshot.
+        /// Default filename is <c>CurrentTest.Name</c> + ".png" when run in test-framework context.
+        /// Using caller method name when run in runtime context.</param>
         /// <param name="superSize">The factor to increase resolution with.</param>
         /// <param name="stereoCaptureMode">The eye texture to capture when stereo rendering is enabled.</param>
         /// <param name="gizmos">True: show Gizmos on GameView</param>
diff --git a/RuntimeInternals/CommandLineArgs.cs b/RuntimeInternals/CommandLineArgs.cs
new file mode 100644
index 0000000..4fd8077
--- /dev/null
+++ b/RuntimeInternals/CommandLineArgs.cs
@@ -0,0 +1,38 @@
+// Copyright (c) 2023-2024 Koji Hasegawa.
+// This software is released under the MIT License.
+
+using System;
+using System.IO;
+using System.Linq;
+using UnityEngine;
+
+namespace TestHelper.RuntimeInternals
+{
+    /// <summary>
+    /// Manage command line arguments for test-helper.
+    /// </summary>
+    public static class CommandLineArgs
+    {
+        internal static string[] CachedCommandLineArgs = Environment.GetCommandLineArgs();
+
+        /// <summary>
+        /// Screenshot save directory.
+        /// Returns <c>Application.persistentDataPath</c> + "/TestHelper/Screenshots/" if not specified.
+        /// </summary>
+        /// <returns></returns>
+        public static string GetScreenshotDirectory()
+        {
+            const string ScreenshotDirectoryKey = "-testHelperScreenshotDirectory=";
+
+            var arg = CachedCommandLineArgs.FirstOrDefault(x => x.StartsWith(ScreenshotDirectoryKey));
+            if (arg != null)
+            {
+                return arg[ScreenshotDirectoryKey.Length..];
+            }
+            else
+            {
+                return Path.Combine(Application.persistentDataPath, "TestHelper", "Screenshots");
+            }
+        }
+    }
+}
diff --git a/RuntimeInternals/CommandLineArgs.cs.meta b/RuntimeInternals/CommandLineArgs.cs.meta
new file mode 100644
index 0000000..d83f840
--- /dev/null
+++ b/RuntimeInternals/CommandLineArgs.cs.meta
@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 75d1e341a0f34380b43ef39e7e2acde6
+timeCreated: 1711029589
\ No newline at end of file
diff --git a/RuntimeInternals/ScreenshotHelper.cs b/RuntimeInternals/ScreenshotHelper.cs
index e7a7f0b..dd0462b 100644
--- a/RuntimeInternals/ScreenshotHelper.cs
+++ b/RuntimeInternals/ScreenshotHelper.cs
@@ -1,10 +1,9 @@
-// Copyright (c) 2023 Koji Hasegawa.
+// Copyright (c) 2023-2024 Koji Hasegawa.
 // This software is released under the MIT License.
 
 using System.Collections;
 using System.IO;
 using System.Runtime.CompilerServices;
-using System.Threading;
 using UnityEngine;
 #if UNITY_INCLUDE_TESTS
 using NUnit.Framework;
@@ -18,10 +17,7 @@ namespace TestHelper.RuntimeInternals
     /// </summary>
     public static class ScreenshotHelper
     {
-        private static string DefaultDirectoryPath()
-        {
-            return Path.Combine(Application.persistentDataPath, "TestHelper", "Screenshots");
-        }
+        private static string DefaultDirectoryPath => CommandLineArgs.GetScreenshotDirectory();
 
         private static string DefaultFilename(string callerMemberName)
         {
@@ -50,7 +46,9 @@ private static string DefaultFilename(string callerMemberName)
         /// <br/>
         /// Using <c>ScreenCapture.CaptureScreenshotAsTexture</c> internally.
         /// </remarks>
-        /// <param name="directory">Directory to save screenshots. Default save path is <c>Application.persistentDataPath</c> + "/TestHelper/Screenshots/".</param>
+        /// <param name="directory">Directory to save screenshots.
+        /// If omitted, the directory specified by command line argument "-testHelperScreenshotDirectory" is used.
+        /// If the command line argument is also omitted, <c>Application.persistentDataPath</c> + "/TestHelper/Screenshots/" is used.</param>
         /// <param name="filename">Filename to store screenshot.
         /// Default filename is <c>CurrentTest.Name</c> + ".png" when run in test-framework context.
         /// Using caller method name when run in runtime context.</param>
@@ -76,7 +74,7 @@ private static string DefaultFilename(string callerMemberName)
             }
             else
             {
-                directory = DefaultDirectoryPath(); // Not apply specific directory when running on player
+                directory = DefaultDirectoryPath; // Not apply specific directory when running on player
             }
 
             Directory.CreateDirectory(directory);
diff --git a/Tests/RuntimeInternals/CommandLineArgsTest.cs b/Tests/RuntimeInternals/CommandLineArgsTest.cs
new file mode 100644
index 0000000..28d2e24
--- /dev/null
+++ b/Tests/RuntimeInternals/CommandLineArgsTest.cs
@@ -0,0 +1,36 @@
+// Copyright (c) 2023-2024 Koji Hasegawa.
+// This software is released under the MIT License.
+
+using System;
+using System.IO;
+using NUnit.Framework;
+using UnityEngine;
+
+namespace TestHelper.RuntimeInternals
+{
+    [TestFixture]
+    public class CommandLineArgsTest
+    {
+        [TearDown]
+        public void TearDown()
+        {
+            CommandLineArgs.CachedCommandLineArgs = Environment.GetCommandLineArgs();
+        }
+
+        [Test]
+        public void GetScreenshotDirectory_WithArgument_GotSpecifiedDirectory()
+        {
+            CommandLineArgs.CachedCommandLineArgs = new[] { "-testHelperScreenshotDirectory=Test" };
+            var actual = CommandLineArgs.GetScreenshotDirectory();
+            Assert.That(actual, Is.EqualTo("Test"));
+        }
+
+        [Test]
+        public void GetScreenshotDirectory_WithoutArgument_GotDefaultDirectory()
+        {
+            CommandLineArgs.CachedCommandLineArgs = Array.Empty<string>();
+            var actual = CommandLineArgs.GetScreenshotDirectory();
+            Assert.That(actual, Is.EqualTo(Path.Combine(Application.persistentDataPath, "TestHelper", "Screenshots")));
+        }
+    }
+}
diff --git a/Tests/RuntimeInternals/CommandLineArgsTest.cs.meta b/Tests/RuntimeInternals/CommandLineArgsTest.cs.meta
new file mode 100644
index 0000000..41f140d
--- /dev/null
+++ b/Tests/RuntimeInternals/CommandLineArgsTest.cs.meta
@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: d5ed4cac644d453f86e05caef8008e79
+timeCreated: 1711031297
\ No newline at end of file