To relate plural cameras at a focal point and to easily change the intersection of convergence even for a moving object by controlling timing to output the image signals of cameras to a monitor among the plural cameras corresponding to the quantity of deviation from a reference position.

A frame control logic 24 applies proper parallax between left and right images and even when there is deviation from a reference point, stereoscopic viewing can be exactly performed without changing the convergence angle of cameras 1 and 2. Timewisely corresponding to outputs from left and right frame memories 22, the images of a left frame 11 and a right frame are formed. Since the frame memories 22 outputs images synchronously with a video synchronizing signal 30, the images of the left and right frames 11 and 12 are alternately displayed on a monitor 5. The frame control logic 24 commands the output timing of the frame memories 22 and this output timing can be set corresponding to the quantity of deviating the position of the object from the reference point.