information regarding the person may be provided as additional conditions used to determine whether face identification is locked consequently a person who does not have to be identified or a person having low importance can be removed from a target of face identification so that face identification is not locked on the person furthermore the registered face is updated at regular intervals yes in step s 9 according to the present embodiment of the present invention face identification lock is unlocked every five fields and the registered face is tried to be updated to the present detected face of the identified person in this instance the time corresponding to u201c five fields u201d between updating the registered face means the fifth field after successful updating if updating is failed whether the registered face can be updated is checked every field if predetermined time has elapsed after successful updating the registered face is updated so long as a predetermined condition is satisfied e g the accuracy of face identification on a detected face at that time is sufficiently high specifically a face identification score is compared to a calculated threshold value which is controlled in accordance with the size and yaw angle of the detected face included in the present frame field step s 10 when the face identification score is higher than the threshold value yes in step s 10 the registered face is updated to the detected face step s 11 as described above the registered face of the identified person is updated to the present detected face every predetermined frame field period consequently the results of face identification can be stabilized over a plurality of frames fields in accordance with a change in the orientation or size of a detected face.