The injection molding employing a mold that includes a molding surface in which a pin hole is formed, and at least one ejector pin that is inserted through the pin hole and that includes an outer peripheral surface facing an inner peripheral surface of the pin hole; includes closing a mold, injecting material into the mold, setting the material, opening the mold, and extruding the material by making a tip end surface of the at least one ejector pin protrude out of a pin hole. The tip end surface is recessed from the molding surface by a predetermined distance in a direction opposite a direction in which the material is extruded, while injecting the material into the mold.