Certification processing hardware is connected to a game apparatus utilized for connecting with a game server in a network game environment to execute a user certification process. The certification processing hardware includes: a storing unit which stores certification information of the user, such as a user ID and a password; a certification information transmitting unit which encrypts the certification information with an encryption key from the game server to transmit it to the game server; a certification result information receiving unit which receives certification result information from the game server; and a certification result decryption processing unit which decrypts the certification result information. Components of the certification information cannot be referred to and copied from outside the certification processing hardware, thereby ensuring the confidentiality of the certification information. Security can be remarkably improved compared to a user certification method in which the user inputs the user ID and password by hand.