To provide a method of machining a multilayer printed board on which highly precise cutting can be conducted by a simple structure, without being affected by the variation in thickness of insulating resin.

In a multilayer printed board 1, the thickness of an insulating layer is measured, the part smaller than the center part of a rectangular part 111 of the insulating layer 3 is scraped off the depth shallower than the upper surface 21A of a guide piece 2A. After an insulating resin layer in only a slight thickness has been left on the upper surface 21A, the insulating resin layer on the guide piece 2A is removed by burning by projecting a laser beam, and the upper surface 21A of the guide piece 2A is exposed. Then, the scraping margin of the insulating layer 3 is measured, using the upper surface 21A of the guide piece 2A as the reference surface, the rectangular part 111 is scraped by a drill pit 15 using the upper surface 21A of the exposed guide piece 2A as the reference surface. The upper surface 21 of the internal layer circuit 2, ranging over the entire area of the rectangular part 111, is exposed.