Injection molding device

An injection molding device comprising an injection structure of a hot runner system for injecting a molding material into a cavity of a fixed mold and a movable mold both clamped,

• the injection structure comprising:
• a hot runner nozzle including a heating part on an outer circumferential side, and a flow path extending from a rear end to a tip in an axial direction and communicating with the cavity;
• and
• a valve pin arranged in the flow path of the hot runner nozzle, the valve pin capable of advancing/retracting in the axial direction, wherein a tip of the valve pin contacts with or separates from a valve opening/closing part provided on a tip side of the hot runner nozzle, thereby closing or opening the flow path,
• wherein a heat insulation groove is provided to an outer circumference of a valve pin contact section, in which the valve opening/closing part of the top nozzle is formed, the heat insulation groove being recessed inward from an outer circumferential surface toward the axial line and extending in a circumferential direction.