PURPOSE: Polyvinylidene fluoride films are laminated with films of a specific dielectric material on the one or both surfaces and electricity is applied to the resulting laminates, thus producing films of polyvinilidene fluoride with high dielectric strength.

CONSTITUTION: On the one or both surfaces of polyvinylidene fluoride film are placed films of dielectric material with a thickness of over 1 micron and an dielectric constant of less than that of polyvinylidene fluoride such as polyethylene or polypropylene and an electric field is applied to the laminate at a temperature lower than the heat decomposition temperature of either the polyvinylidene fluoride or the dielectric film, preferably a temperature lower than melting or softening points so that the strength of electric field on the polyvinylidene fluoride film is made over 10 KV/cm but lower than the dielectic strength, thus producing polyvinylidene fluoride films with dielectric strength of over 100MV/cm at room temperature and over 8 MV/cm at 100°C.