A personal authentication apparatus comprises an input unit configured to input image data; a face detection unit configured to detect a face region of a person included in the image data input by the input unit, and to detect feature data from the detected face region; a facial expression determination unit configured to determine a facial expression from the face region detected by the face detection unit; a storage unit configured to store feature data used to authenticate a person in correspondence with respective facial expressions of a plurality of faces; a selection unit configured to select feature data corresponding to the facial expression determined by the facial expression determination unit from the storage unit; and an authentication unit configured to authenticate a person by comparing the feature data of the detected face region, and the feature data selected by the selection unit.