By composing a cooling channel just near the mold surface using the milling-combined laser metal sintering method, cooling during injection is promoted and the cooling time is reduced. In order to evaluate this effect, a cone with ribs inside the upper part is picked up. A spiral-cooling channel is fabricated along the side surface of the mold core and also between the ribs in the upper part. To compare with this, a steel mold with machined baffle channels was made. The diameter of the upper part of the molded cone was chosen as an evaluation dimension. The temperature on the upper surface of the core is kept low at around the cooling water temperature in the case of sintered mold during the cycle of the injection. On the other hand, the temperature on the upper surface of the steel mold increases far higher than the cooling water temperature. Cycle time for the same shrink ratio in the upper part of the molded cone was 25 s in the sintered mold and 40 s in the steel mold. Owing to the cooling time reduction, cycle time of the injection molding was reduced 35% by using the sintered mold with cooling channels. Simulation is available to evaluate the mold temperature distribution and is useful for improving the arrangement of cooling channels in the process of mold design.