Subsequently, the user identification means 105 compares the feature value obtained by the feature extraction means 104 with the feature value of at least one registered user stored in the feature value storage means 106 beforehand, to determine whether or not the user to be authenticated corresponds to the registered user (step S105). The user identification means 105 may use any of one-to-one authentication and one-to-N authentication as the determination method, where N is an integer of 1 or more.

In the case of using one-to-one authentication, the user identification means 105 compares the feature value of the user to be authenticated (the feature value obtained by the feature extraction means 104) and the feature value of a registered user, on a one-to-one basis. Here, the administrator of the personal authentication device may designate, to the user identification means 105, which registered user is subjected to comparison, using a user ID or the like beforehand. In the case of using one-to-one authentication, for example, the user identification means 105 may calculate the distance between the feature value of the user to be authenticated and the feature value of the designated registered user, and determine that the user and the registered user are the same person in the case where the distance is less than a threshold. The user identification means 105 may determine that the user and the registered user are different persons, in the case where the calculated distance is more than the threshold.