To improve authentication accuracy against any change in a state of a face area, with a small processing load.

When performing authentication, a face detection part 102 detects a face area from each frame in image data and outputs associated detection data including face direction information in the face area. A characteristic data generation part 104 extracts characteristic data from a face area and a registration determination part 801 determines whether or not the characteristic data is appropriate as an object of additional registration according to the associated detection data. An authentication part 106 performs authentication processing by comparing registered characteristic data in a personal database 108 with the extracted characteristic data. The authentication part and a registration part 109 register the characteristic data corresponding to a face area in a second frame in the personal database part, when the characteristic data is determined to be appropriate as an object of additional registration by the registration determination part, and if the characteristic data has been specified as the same face area as that of a first frame but authentication has not been performed in the second frame which succeeds the first frame in which authentication was performed by a tracking part 105.