PURPOSE: To eliminate connection failure between a connection via and a surface pattern by providing a conductor thin film for electrode on a single surface of a ceramic insulating base after grinding both surfaces, by forming a subsidiary conductor which is combined with the connected via by the use of metal plating, and then grinding both surfaces again for eliminating the conductor thin film and a part of the subsidiary conductor which protrudes from the surface.

CONSTITUTION: A plurality of green sheets 1 where an inner-layer pattern 3 is printed are laminated, a ceramic insulation base 4 where a connection via 2 is placed by calcination, both surfaces are ground to enable pull of the connection via 2 and a void to be exposed on the surface, and a thin film of copper-nickel plating is provided on a single surface of the ceramic insulting base 4, thus forming a conductor thin film 16 which is connected to the connection via 2. Then, copper plating is performed to the conductor thin film 16 and the connection via 2 with the conductor thin film 16 as - electrode, thus forming a subsidiary conductor 17 at the pull of the connection via 2 and the void part. Both surfaces are ground again to eliminate the conductor thin film 16 of copper-nickel and the part protruding from the surface of the subsidiary conductor 17 is eliminated for forming a plane.