PURPOSE: To produce a reliable through hole connected conductive circuit without defects by coating a through hole and the vicinal conductive layer with an Ni plating film, forming the mask made of a photoresist film and forming the conductive circuit.

CONSTITUTION: An Au film is formed on the front and the rear planes of a substrate 1 and on the inner wall of a through hole 2 as a conductive layer 3, an Au plating film is formed and a conductive layer 4 in which the conductive layer 3 is included is formed. Then, a plate resist film 5 is applied on the part other than the through hole and its periphery, an Ni plating film 6 is provided only on the through hole and its periphery and the plate resist film 5 is removed. Photoresist is coated on the Ni plating film of the through hole and its periphery and a photoresist film 7 of the desired pattern is formed. The Au film 4 is etched by using the film 7 as a mask, the Ni plating film 6 is dissolved by nitric acid, and a film circuit substrate whose front and rear planes are connected by the Au film at the through hole is produced.