PURPOSE: To prevent a base film from being shrunk when a circuit pattern is formed or when an overlay is bonded by a method wherein a metal layer for shrinkage prevention use is formed on the face on which the circuit pattern is not formed of the base film.

CONSTITUTION: At a flexible printed wiring board, a circuit pattern 2 is formed on the surface of a polyimide film 1 as a base film after an etching treatment has been executed to a metal conductor layer, and a copper foil 3 in a grid pattern shape is formed on its opposite face. Within an arbitrary arange of 1cm×1cm, the area occupied by the metal layer 3 is 50% or higher. Parts (the film 1) which are not backed with the metal layer 3 are surrounded by the metal layer 3 and are formed as respectively independent small areas. As a result, the shrinkage of the film 1 in the parts can sufficiently be suppressed.