At a filling termination stage when performing multi-layer molding by means of a hot runner nozzle, an intermediate layer in a multi-layer molded article is prevented from being formed in a shape causing the intermediate layer to enter into a sprue in a portion of a mold cavity in a mold corresponding to the sprue. The multi-layer molded article with no intermediate layer being exposed in a sprue cut portion can be therefore obtained. In this manner, a diameter of a discharge port opening and closing mechanism part for opening and closing the resin discharge ports in the shut pin is made different from a diameter of a nozzle gate opening and closing mechanism part configured of the projection for pushing out the molten resin in the nozzle gate.