It is possible to prevent use of a forged card. An authentication chip describing information which cannot be copied or difficult to be copied is attached to a card and a card processing device includes a card authentication processing device. The information described in the authentication chip is degitized and encrypted to obtain encrypted data, which is described on an authentication certifying chip. The authentication certifying chip is attached to the card. The authentication certifying chip checks the validity of the authentication chip. Before a specific operation such as entry of a password is started, it is judged whether the card is true so as to exclude a forged card.