An image obtaining section 106 obtains an imaged image from an imaging device. A face authenticating section 132 detects a face image of a registered user present in the imaged image using face identifying data retained in a registered user information retaining section 180. A damage determining section 142 determines whether or not the face identifying data read from the registered user information retaining section 180 by a face data reading section 130 is damaged. If the face identifying data is determined to be damaged, a notifying section 144 notifies that the face identifying data is damaged.