PURPOSE: To correctly obtain the drilling position of a printed circuit board in the drilling using the X-ray.

CONSTITUTION: A printed circuit board is irradiated with the X-ray from an X-ray irradiating means, the transmitted image of the identification mark provided on the printed circuit board is photographed (72) by an X-ray camera, and this result is image processed to detect the center position of the mark (73). A drilling means is moved (74) so as to be opposite to this mark center position to achieve the drilling (75). Then, the identification and the hole are simultaneously photographed (76) and both positions are compared with each other (77). If both positions are deviated from each other, the corrective data are prepared based thereon. The images M, H of the identification mark and the hole are simultaneously photographed after the drilling, and the results are used as the corrective data. Because the deviation attributable to the movement of the work in the drilling operation is eliminated, drilling can be made at the correct position in the subsequent drilling operation.