The object of the present invention is to provide a gas barrier film suitable for medical uses, which is excellent in gas and vapor properties and can prevent ingredients of an adhesive and the like from eluting even after heating and sterilizing treatment, and a medical bag using the gas barrier film. A medical gas barrier film of the present invention comprises a multilayer gas barrier film 10 including a deposition oriented polyester layer 11 having a deposited layer 13 of an inorganic oxide on one surface, an oriented polyamide layer 15 adhered to the surface of the deposited layer 13 and a polyethylene layer 17 adhered to the surface on the opposite side to an adhered surface 15a of the oriented polyamide layer 15, and a multilayer substrate film 22 including a cyclic olefin polymer layer 25, an elastomer layers 24, 26 and a heat sealing layer 23, and the multilayer substrate film 22 is adhered to an other surface 11b on the opposite side of the deposited layer of the deposition oriented polyester layer 11.