PURPOSE: To inhibit the generation of cracks or void and at the same time prevent the edge of a drill from being cut or bent by installing a dummy land to a clearance hole and a central hole which matches with the diameter of a through hole to the central part of the dummy land.

CONSTITUTION: A ring-like dummy land 12, whose outer periphery is smaller than a clearance hole 11 is formed at the central position of the clearance hole 11. The dummy land 12 is provided with a central hole 12a slightly larger than a drilled hole used as a through hole 2. On the other hand, there are formed patterns for the other intermediate layers 5 provided with a land 13 or the like for a copper-clad laminated board. Then, each intermediate layer 5 which includes a metal sheet layer 1m is laminated with a prepreg 6 clamped between each layer and produced together with the surface layer so that the resin submerged into a glass core material of the prepreg 6 is filled into the clearance hole 11. At that time, the dummy land 12 forms a barrier preventing the flow of the resin so that the resin may spread over the peripheral parts to a satisfactory extent. Furthermore, a drilled hole 2a, which serves as the through hole 2, is bored at a specified position by drilling work.