METHOD FOR MACHINING PRINTED CIRCUIT BOARD

In order to enable the determination of a center precisely and automatically, a reference mark on a printed circuit board is image-recognized to determine tone transition points, thereby to determine an interim center and diameter of the mark by a four-points searching method. Next, a preset minute value .alpha. is added to the interim mark diameter to determine a standard circle diameter, thereby to set a standard circle having the interim center as its center. Then, image processing is performed in that standard circle and the mark is separated into a plurality of sections. The center of the mark is detected by determining the center of the section of the tone indicating the mark. Machining operations such as the perforations are carried out on the basis of the detected center.