To obtain a wide visual field and a tracking error signal with good response and high precision by performing specific operation on the basis of an electric quantity read out of an image pickup element and setting an area where the electric quantity is read out on the basis of position information and size information of a target image on an image pickup plate.

This device has the same constitution as before except a readout area setting circuit 7. An arithmetic circuit 6 outputs the position information and size information of the target image on the image pickup plate. According to the output information, the area setting circuit 7 sets an area which has arms radius (a) and is, for example, four times in size around the gravity center position (Xc, Yc) in consideration of the movement quantity of a tracking target or the shape, light quantity distribution, etc., of the target image as a readout area. Noise components that the read electric quantity contains can be made small and the read time can be shortened by horizontally transferring only the readout area at a low speed. When the read electric quantity is less than a threshold value, the target image area is divided into four quadratures and the target is traced by a light quantity center method.