PURPOSE: To discriminate whether the shape and size of various products are within specified range or not with a simple constitution and operation, by comparing the detected output of the reference inspected object pick up stored in the memory and the detected output at inspected object pick up.

CONSTITUTION: The reference inspected object is prepared in advance, this is picked up with the camera 11, and the optical image is pictured on the monitor television 12. On the other hand, the measuring range of arbitrary horizontal and vertical size of screen of the monitor television 12 is reproduced by adjusting the measuring range specified signal set circuit 13. The video signal from the camera 11 and the measuring range specified signal from the set circuit 13 are fed to the overlap width measuring circuit 14, the output signal is stored in the memory 15, and the signal stored in the memory 15 and the detected output at inspected object pick up are compared at the comparison circuit 16, and the propriety of inspected object is discriminated whether the difference of the both signals is within permissible range or not.