OBJECTIVE A user is prevented from inadvertently inputting authentication information to an unauthorized authentication system. In this manner, authentication information leakage is certainly avoided. SOLUTION A validity checking system includes an information processing card, an authentication system that performs mutual authentication with the information processing card, and a checking device. The information processing card includes a validity authenticating means that authenticates the validity of the authentication system, and an impersonation preventing means that carries out an impersonation preventing process on the result of the authentication performed by the validity authenticating means. The checking device includes a verifying means that verifies the authentication result subjected to the impersonation preventing process and is output from the information processing card, and a verification result output means that outputs the result of the verification performed by the verifying means to a user in a perceptible manner. The verifying means may not be provided in the checking device, and an independent verification device may be provided.