To provide a secure and inexpensive authentication system for personal authentication.

The authentication system includes an authentication database 42 for storing and correlating biometric authentication data 111, a user ID 410 and a door ID 311; an authentication server 4 for transmitting the user ID 410 corresponding to biometric authentication data 111 transmitted from a portable terminal 1 to the portable terminal 1 on the basis of the authentication database 42; and a door section 31 having an open/close operation function for transmitting the user ID 410 transmitted from the portable terminal 1 to the authentication server 4 after adding the door ID 311 thereto and for controlling the open/close operation of the door on the basis of an authentication result transmitted from the authentication server 4. The authentication server 4 conducts authentication for the user ID 410 and door information transmitted from the door section 31 on the basis of the authentication database 42 and transmits the authentication result to the door section 31.