A likelihood of each of a plurality of registered images belonging to a same group for an input image is calculated, and a prescribed number of registered images is selected from a top ranking in descending order of likelihood among the plurality of registered images as the authentication result for the input image. Based on a likelihood of a registered image included in an authentication result for an input image of a first frame and a likelihood of a registered image included in an authentication result for an input image of a second frame being previous to the first frame, one of the authentication result for the input image of the first frame and the authentication result for the input image of the second frame is displayed.