To provide an authentication method, an authentication system, a server for the authentication system, and a recording medium by which a game machine 3 in a game center, an automatic lending machine of audio-visual information recording media in a store or a device such as an accompaniment instrument can be utilized only by a portable terminal 1 and a member's card even when a user has no money with him (or her), and even when either one of the portable terminal 1 and the member's card is lost, the lost article is not ill-used.

Since AND between information from the portable terminal 1 and information stored in the member's card which is a non-negotiable value card is found out, security is secured. Accordingly, even when either one of the portable terminal 1 or the member's card is lost, the lost article is not ill-used.