There are provided two types of moistureproof films of a laminated structure. The first type of moistureproof film comprises a core layer (A) and a protective layer (B) joined to one side of the core layer, wherein: (a) the core layer (A) is composed of a transparent film of a polyvinyl alcohol having a degree of saponification of 99 mol % or higher, the film having a silicon oxide thin film formed on at least one side thereof; and (b) the protective layer (B) is composed of a transparent film including at least one layer of a transparent plastic film having a transparent silicon oxide thin film formed on at least one side thereof. The second type of moistureproof film comprises a moistureproof film of a laminated structure comprising a core layer (A), a protective layer (B) joined to one side of the core layer and a sealant layer (C) joined to the other side of the core layer, wherein: (a) the core layer (A) is composed of a film of a polyvinyl alcohol having a degree of saponification of 99 mol % or higher, the film having a silicon oxide thin film formed on at least one side thereof; (b) the protective layer (B) is composed of a transparent film including at least one layer of a transparent plastic film having a transparent silicon oxide thin film formed on at least one side thereof; and (c) the sealant layer is composed of a sealable resin.