The present invention provides a printed wiring board which has high insulation resistance between wirings and is unlikely to cause failures such as leakages or short circuits, attributable to ion migration even in high temperatures and highly humid environments. The printed wiring board has a circuit comprising a metal conductor on base metal layers created by forming an insulating resin layer 4 on at least one face of an insulating substrate 1 and forming the base metal layers 2 and 5 on the insulating resin layer. In the printed wiring board, at least a part of an upper face of the insulating resin layer existing in spaces 11 between the metal conductors is formed at a position lower than the interface between the base metal layer 5 and the insulating resin layer 4.