PURPOSE: To test a device in a wafer state with high accuracy even when a wafer diameter becomes large.

CONSTITUTION: The focal distance of a photographing apparatus 20 which takes the picture of a wafer surface is set in such a way that a prescribed part on the photographed wafer surface can be focused when a wafer 1 on a stage 2 is situated in a prescribed height position. At each device which is tested, the height of the stage is adjusted, on the basis of the result of the image processing operation of an aluminum mark part whose height is the same as that of a pad, in such a way that the aluminum mark part is focused. The pad of each device is brought into contact with a probe needle 3.