The invention provides a gas barrier film with low deterioration in the gas barrier property before and after high-temperature hot water treatment. The gas barrier film has a gas barrier coating film, formed as a composite film comprising a network structure having a mesh structure with Si-O-Si bonds as the basic lattice and a water-soluble polymer crystallized as microcrystals, incorporated into the mesh of the network structure, wherein a barrier coating agent, obtained by mixing a condensate solution of an alkoxysilane hydrolysate prepared as a mixed solution in which the proportion of bonded states of the silicon atoms of the condensate with Q1 and Q2 structures is at least 60% of the total silicon atoms, with a crystalline water-soluble polymer, is coated on a base material film, either after forming or without forming an aluminum oxide vapor deposition film, to form a coating layer.