An authentication device authenticates a user using biometric information. The authentication device including: a storage unit, a first acquisition unit, a second acquisition unit, a controller, an authentication processing unit, and an update processing unit. When the first acquisition unit acquires identification information, and a combination for which the number of successes for the acquired identification information is greater than or equal to a predetermined number is present in combination information, the controller sets a threshold such that a false acceptance rate for erroneously authenticating a person other than a registered user becomes lower than when the combination is not present.