A method for producing a semiconductor package is a method for producing a semiconductor package in which a plurality of semiconductor chips, each of which includes a substrate, conductive portions formed on the substrate, and microbumps formed on the conductive portions, are laminated, which includes a heating process of causing a reducing gas to flow in an inert atmosphere into a space where the semiconductor chips are arranged and heated at or higher than a temperature of a melting point of the microbump, and in the heating process, a pressure application member is mounted on the microbump.