1. An apparatus for managing a Unity file in a mobile platform including: a file extracting section that extracts a Unity library file from a Unity application; an encrypting section that encrypts a programming library file in the Unity library file thus extracted and creates an encrypted programming library file; a file creating section that creates a decrypting library to decrypt the encrypted programming library file and creates a secured Unity application using the decrypting library and the encrypted programming library file; and a file executing section that, upon request to execute the secured Unity application, executes the secured application by decrypting the encrypted programming library file using the decrypting library.