A laminate that improves barrier properties of an atomic layer deposition film in spite of use of a substrate made of a polymer material, and provides a gas barrier film and a method of producing the same. The laminate includes: a substrate made a polymer material; an undercoat layer disposed on at least part of a surface of the substrate and made up of an inorganic material containing Ta; and an atomic layer deposition film disposed so as to cover a surface of the undercoat layer.