A resin injection molding method of molding a resin by injection-filling an inside of a mold cavity formed by mold-clamping a pair of a design surface mold and a non-design surface mold, with a melted thermoplastic polypropylene resin composition, the method including: setting a temperature of each cavity-forming surface of the design surface mold and the non-design surface mold prior to the injection filling to 60° C. to 120° C., with the temperature of the cavity-forming surface of the design surface mold being 5° C. to 50° C. higher than the temperature of the cavity-forming surface of the non-design surface mold; and causing the resin pressure to reach a negative pressure within 7 seconds after injection filling is complete, wherein the thermoplastic polypropylene resin composition contains a crystalline polypropylene resin and a rubber component and a content of the rubber component is 1 mass % to 40 mass %.