To provide an illumination nonuniformity collecting method which eliminates the need for adjusting the location of an illumination system and the angle of illumination and is capable of obtaining stable detection results easily.

This illumination nonuniformity collecting method is used at the time of detecting an object illuminated by an illumination system 1 through the use of an image pickup device 6. A white plate 13 is placed in the visual field 8 of the image pickup device 6, and the white plate 13 is illuminated by the illumination system 6 to obtain luminance distribution in advance. After removing the white plate 13, an object is carried onto a moving table 10 into the visual field 8 of the image pickup device 6, then the moving table 10 is moved to move the object automatically to the place 15 of the maximum luminance level obtained from the luminance distribution.