PURPOSE: To stabilize the system by holding the state or a gate means based on that the just preceding position set information outputted last is correct in the case of a short-time error.

CONSTITUTION: A gate circuit 261 in an AF evaluation value processing circuit 26 and a gate circuit 251 in a diaphragm control circuit 25 which take out a picture signal corresponding to a prescribed area in the screen, a line of sight detecting block which inputs position set information to indicate the set position of the prescribed area in the screen, a frame generating circuit 27 and a microcomputer 29 which controls the position of the prescribed area in the screen, and the frame generating circuit 27 and the microcomoputer 29 which keep the prescribed area in the state just before the occurrence of error in the case of the occurrence of error in the position setting operation of the prescribed area are provided. Thus, the operation state is not immediately changed when error occurs in the line of sight detecting block; and in the case of a short-time error, the state of the gate circuit 261 is held based on that the just preceding position set information outputted last is correct, thus stabilizing the system.