The longest process in the injection molding process is the cooling process of the molded product. Therefore, shortening the cooling time is key to reducing the injection molding cycle time. For fast cooling time, the production of conformal cooling channels using metal 3D printing instead of the conventional linear cooling channels is continuously increasing. In this study, the cooling effect of the conventional linear cooling channel application and the conformal cooling channel application using metal 3D printing was compared in the design of the back cover molding mold of the circulator that has been widely used recently. The comparison of the cooling effect was based on the mold temperature and the molded product temperature for a certain period of time after completion of molding. It was confirmed that the time required to eject from the mold with the conformal cooling channel to the ejecting temperature of the molded product was reduced by 28.7%, and the maximum temperature of the mold was also reduced by 40%.