PURPOSE: To enhance adhesive strength to a prepreg and a circuit part and to improve the efficiency of inspection of a circuit by a black automatic optical inspecting unit by roughing both surfaces of a copper foil formed with a circuit pattern of an inner layer circuit board, and blackening the roughed surfaces of the prepreg side.

CONSTITUTION: Metal for roughing in plating needs properties of not corroding with acid, or alkaline reducing chemical at the time of through hole plating to prevent haloing, and includes, for example, copper, nickel, chromium, and/or their alloys. When one or more types of these metals are further plated and roughed on the roughed surface of the foil, extremely fine uneven shape is formed by regulating plating conditions to form black external appearance. It is necessary to be fine in the degree of not reflecting visible light, and the size of the uneven surface is normally 100-10,000 angstrom. After a copper-clad laminated board for an inner layer circuit board is formed by using the copper foil provided on the roughed surface of a multilayer forming prepreg side of both side roughed copper foil, the inner layer circuit is formed by a known etching method as an inner layer circuit board.