In view of the problem stated above, the present invention has an object of providing a personal authentication device, a personal authentication method, and a personal authentication program that lessen a psychological and/or physical burden on a user to be authenticated.

A personal authentication device according to the present invention includes: acoustic signal transmission means for transmitting a first acoustic signal to a part of a head of a user; acoustic signal observation means for observing a second acoustic signal which is an acoustic signal after the first acoustic signal propagates through the part of the head; acoustic property calculation means for calculating an acoustic property from the first acoustic signal and the second acoustic signal; and user identification means for identifying the user, based on the acoustic property or a feature value extracted from the acoustic property and relating to the user.

A personal authentication method according to the present invention includes: transmitting a first acoustic signal to a part of a head of a user; observing a second acoustic signal which is an acoustic signal after the first acoustic signal propagates through the part of the head; calculating an acoustic property from the first acoustic signal and the second acoustic signal; and identifying the user, based on the acoustic property or a feature value extracted from the acoustic property and relating to the user.