diff --git a/SS2301-03/ss2301-03.cpp b/SS2301-03/ss2301-03.cpp
index e69de29..533fe32 100644
--- a/SS2301-03/ss2301-03.cpp
+++ b/SS2301-03/ss2301-03.cpp
@@ -0,0 +1,39 @@
+#include <iostream>
+#include <fstream>
+#include <vector>
+
+bool is_binary(const std::string& filename) {
+    std::ifstream file(filename, std::ios::binary);
+    if (!file) {
+        std::cerr << "Cannot open file: " << filename << std::endl;
+        return false;
+    }
+
+    char ch;
+    while (file.get(ch)) {
+        // ヌルバイトが含まれている場合はバイナリとみなす
+        if (ch == 0x00) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+int main(int argc, char* argv[]) {
+    if (argc < 2) {
+        std::cerr << "Usage: " << argv[0] << " <file1> <file2> ..." << std::endl;
+        return 1;
+    }
+
+    for (int i = 1; i < argc; ++i) {
+        const std::string filename = argv[i];
+        if (is_binary(filename)) {
+            std::cout << filename << ": Binary file" << std::endl;
+        } else {
+            std::cout << filename << ": Text file" << std::endl;
+        }
+    }
+
+    return 0;
+}