To provide an authentication system capable of confirming reliability of a user.

The authentication system, which provides information on merchandise and service via a network and connects transaction information inputted from a user terminal to an information provider, is provided with a means 10 for arbitrarily setting whether or not the information provider acquires the user's transaction information, a user registration means 7, a means 6 for managing the registered data or the like, a means 11 for performing identification and authentication of a general user or a registered user, and a means 12 for transmitting only the transaction information inputted from a registered user to the information provider by arbitrary setting the information provider based on the result of the authentication.