In vented injection molding, since deaeration of the water / volatile gas is performed from the resin in the molten state from the vent hole provided in the cylinder in the vent hole type injection molding, the drying step of the raw material essential in the non-vent type is omitted. In dry-free forming, the concern is degradation of physical properties due to hydrolysis. Depending on the manufacturer, this resin is required to dry the material. However, now when it comes out of the dryer, resorption of the resin begins. In the vent molding, it is an idea that water or volatile gas is discharged from the molten state, so drying does not matter. Since it is evacuated from the vent hole, it is unnecessary to consider preliminary drying / re-absorbing water. In this study, when introducing vent type injection molding, it is evaluated whether or not a molded article without physical property deterioration can be obtained. The resin used in this experiment is a polycarbonate material (PC) which is susceptible to hydrolysis.