To prevent heat generating performance from being damaged in spite of long term preservation and also to enable incineration-processing by using a base stock film where at least a metallic compound is coated in an air- nondiffusible packing material as a base material for the air-nondiffusible bag of the heat generating body which generates heat under the existence of air.

The air-nondiffusible packing material is constituted by successively laminating a metallic compound layer 2, an adhesive layer 3 and a sealant layer 4 on the base stock film 1. A flexible resin film such as polyethylene, polypropylene, polyester and nylon, favorably, a polyethylene terephthalate film is used as the base stock film 1. The metallic compound layer 2 is arranged as the layer for giving water vapor barrier property and oxygen barrier property and aluminum oxide and silicon dioxide are used for it. Then, water vapor permeability and the small amount oxygen permeability of the base stock film 1 which is coated by the metallic compound layer 2 are respectively set to be equal to below 1 g/m2.day and to be equal to below 1 ml/m2.(day.101.325 kPa.