PURPOSE: To be used as a packaging material for preventing mildew of food or the other and to perform a mildewproofing effect by forming a resin layer containing specific substance on one surface of a gas impermeable film, and laminating a gas impermeable film thereon.

CONSTITUTION: A resin layer containing adsorption carrier for carrying 0.05-20wt.% of alkaline metal salt or alkaline earth metal of chlorous acid and aqueous solution having pH of 7.5-13.0 or preferably a chlorinated polypropylene resin layer is formed on one surface of a gas impermeable film or a gas semi-permeable film. A gas permeable film made of a polypropylene film coated with vinylidene chloride resin or a gas permeable film having larger gas permeability than that of the gas semi-permeable film is preferably laminated thereon. When such a film is used, it is so disposed that the gas permeable film is disposed on its inner surface.