An authentication device enabling access from multiple directions, comprises a biometric information acquirer that acquires biometric information from a biometric target; a detector that detects direction of access by the biometric target; a memory that stores in advance therein a template for authentication; and an authenticator that authenticates the biometric target on the basis of the detected access direction information of the biometric target, biometric information acquired from the biometric target, and the template. The authenticator performs authentication using access direction information for the biometric target by carrying out conversion of acquired biometric information or the template, so that the access direction at the time of biometric information acquisition matches the access direction at the time the authentication template was acquired.