To provide an authentication system whose security is high.

This system is provided with not only a Web server 9 which provides contents but also a voice recognition server 4 which authenticates the voice of the user of a personal computer 11 who has performed access to the Web server 9. Also, a service center 3 is provided with an authentication DB server 6 which manages a voice authentication database 13 in which the combination of question sentences and answers set by a registered user is stored. Then, the voice recognition server 4 receives the combination of the question sentences and answers from the authentication DB server 6 in response to an access from a portable telephone 1 of the user, and carries out voice authentication to the portable telephone 1. When authenticating that the user is a normal registered user, the voice recognition sever 4 transmits the effect to the authentication DB server 6. When a voice authentication state being the authentication result of the user is requested from the Web server 9, the authentication DB server 6 transmits the voice authentication state to the Web server 9.