Abstract: An injection molding method for a polyamide resin molded article in which an already-molded article including a polyamide resin is set in a molding die and, then, the polyamide resin, which has been heated so as to be in a molten state, is injection-filled in a cavity to which a part of the already-molded article faces thereby integrally molding an additional molding part onto the part of the already-molded article. A primer is applied to a predetermined integral molding part, and then the thus primer-applied already-molded article is set in the molding die. The primer includes an alcohol solution containing the polyamide resin and a chemical that is capable of dissolving the polyamide resin.