PURPOSE: To make thinner the copper film on a surface layer thereby enabling fine patters to be formed by limiting the coating step of Cu conductive film on the surface of a surface layer to only one time.

CONSTITUTION: A surface layer and a Cu foiled insulating substrate as an interior are bored after the lamination to form a through hole. Next, the first Cu conductive film 4 is coated by electroless plating step. Next, only one surface to be the surface layer is coated with the first sensitive layer 5 to be irradiated with active rays. Next, the surface layer and the inside of the through hole not coated with the first sensitive layer 5 are coated with the second Cu conductive film 6. Next, after the removal of the first sensitive layer 5, the first and second conductive films 4, 6 are coated with the second sensitive layer 7. Next, regular resist patterns 8 are formed by exposure and development. Finally, the Cu circuit patterns are to be formed by etching step.