Injection molding apparatus

An injection molding apparatus, comprising:

• 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,
• wherein the injection molding apparatus extrudes the material by making a tip end surface of the at least one ejector pin protrude out of the pin hole, after closing a mold, injecting material into the mold, setting the material, and opening the mold,
• wherein, while material is injected into the mold, a recess portion is formed in a portion of the molding surface that corresponds to the tip end surface of the ejector pin by recessing the tip end surface of the ejector pin from the molding surface by a predetermined distance in a direction opposite a direction in which the material is extruded, and
• wherein, when the predetermined distance is designated as Y (mm) and a number of times that a molded article is molded by injecting the material into the mold is designated as N (times), the predetermined distance satisfies the expression Y=7.98×10−5N−0.039.