PURPOSE: To reduce a bridge in the case of patterning by removing a resin film adhered to a surface of a copper layer provided on an insulating substrate by etching with resin etchant, and further mechanically polishing the surface.

CONSTITUTION: Copper layers 2 are provided on both side surfaces of a laminated substrate 1. Then, resin films 3 adhered to the surface of the layer 2 is removed by resin etching, and completely cleaned by mechanically polishing with a polishing brush 4. Thereafter, a dry film is thermally press-bonded to the surface of the layer 2, then exposed, developed, and patterned to form an etching resist film 5. Subsequently, with the film 5 as a mask the layer 2 is removed by etching, the film 5 is then peeled, and a circuit 6 is formed. Thus, the number of bridges generated in the case of patterning the circuit 6 can be reduced.