To provide a gas-barrier film laminate having heat-treatment resistance which can keep initial gas-barrier properties even when subjected to heat treatment by heat sterilization, cooking, or the like.

A vapor deposition membrane layer of an inorganic oxide and a gas-barrier composite film layer produced by heating/drying a thin coating film made of a coating agent mainly containing an aqueous solution or a water/alcohol mixed solution containing a water soluble polymer and at least one metal alkoxide or its hydrolyzate are formed on at least one surface of a plastic substrate, and a barrier-deterioration preventing layer comprising a polyurethane resin material added with an inorganic compound is formed further on the composite film layer.