An authentication device that authenticates a user using person specifiable information includes a first storage unit configured to store person specifiable information specifying a registered user, a second storage unit configured to store association information in which the registered user is associated with a predetermined terminal possessed by the registered user, a first acquisition unit configured to acquire person specifiable information from an authentication target user, a second acquisition unit configured to acquire identification information, a user specifying unit configured to specify a user associated with the terminal transmitting the identification information based on the association information and the identification information, and an authentication processing unit configured to authenticate the authentication target user by executing a comparison process between the person specifiable information of the authentication target user and the person specifiable information of the registered user in an order that is set based on the specified user.