PURPOSE: To obtain a recess detecting method which can automatically detect the recessed part in the upper surface of a material under inspection positively.

CONSTITUTION: The upper surface of a lead pattern 11 is lit with a lighting device 12 which emits luminous flux at the depression angle of about 30° with respect to the above described upper surface. The image of the reflected light from the lead pattern 11 in the lighting region of the lighting device 12 is picked up with an image sensing camera 15. The picked-up image is processed with an A-D converter 17, a first comparator circuit 20, a second comparator circuit 22 and image operating circuits 23 and 24. Thus, the presence or absence of the recessed, part in the upper surface of the lead pattern 11 is automatically judged.