PURPOSE: To eliminate an exposure of a copper plate on the end surfaces of the title board cut in the size of a product by a method wherein the copper plate is divided into the part, which is located on the inner side of a product external shape line, of the plate and the part, which is located on the outer side of the line, of the plate and an insulator is filled between the division over a range apart a prescribed distance form the line on at least the inner side of the line at the time of lamination.

CONSTITUTION: Grooves 3 having a prescribed spreading are intermittently formed in a copper plate 1 prior to the lamination of prepregs on the inner side and the outer side of a product outline 2 along the line 2 and the prepregs 4 are respectively piled on both surfaces of the plate 1. Residual parts 5 left between the grooves 3 are removed along with the laminated prepregs 4 and there is the need for making the residual parts 5 and the grooves 3 continue completely. Then, another prepregs 4 are respectively laminated from both sides of the plate 1 and the prepregs 4 are filled in parts, from which the grooves 3 and the parts 5 are removed. When a multilayer printed board provided with this built-in copper plate is cut along the line 2, the prepregs 4 filled in the parts of traces, from which the grooves 3 and the residual part 5 are removed, appear on the cut surfaces, the peripheral edges of the plate 1 on the inner side of the board are insulated from the outside by these prepregs 4 and a process for coating an insulator on the end parts of the board after the external shape of the product is cut can be omitted.