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.