A person authentication apparatus (20) generates one or more second image sequences (50) by applying a predetermined time-series operation to a first image sequence (40) acquired from a camera (10). The person authentication apparatus (20) extracts, from each of two or more image sequences among the first image sequence (40) and the second image sequence (50), a gait feature of a person included in the image sequence. The person authentication apparatus (20) performs authentication of a person by comparing the plurality of extracted gait features with a verification feature stored in a verification database (30).