PURPOSE: To shorten a molding cycle by preventing the accumulation of heat in a core pin to enhance the productivity of molding.

CONSTITUTION: In an injection mold performing injection molding by injecting a resin material into the hollow part formed by a core 4 equipped with a core pin 3 of which the leading end part is fitted in the recessed part 2 of a product 1 and the cavity 5 provided in opposed relation to the core 4, the core pin 3 is composed of a material having predetermined hardness and good heat conductivity and the end part on the side opposite to the leading end part of the core pin 3 is forcibly cooled. By this constitution, the productivity of a molded product can be enhanced.