PURPOSE: To obtain the stable pressure rising characteristic of a pressurizing cylinder regardless of the unevenness of molten metal supplying quantity by executing a change- over command from the injecting fill-up to the pressurize operation at the timing when the load value detected with torque of a motor reaches a prescribed value.

CONSTITUTION: An injection device 3 is shifted to the molten metal pouring position, and after pouring the molten metal into an injection sleeve 17, the device is returned back to the injecting position. Successively, oil is fed into a cylinder 12 to ascend a ram 8, sleeve frame 15 and an elevating shaft 13, and the injection sleeve 12 is joined with a fixing sleeve of the die, A motor is started to rotate a screw shaft 21 through a bevel gear 25, and at the time of ascending a supporting frame 18 with the action of a ball screw 32, the integral plunger tip 24a is ascended. The molten metal in the injection sleeve 17 is injected into the cavity in the die. The loaded torque of the motor is quickly increased just before completing the fill-up of molten metal, and at th time of rising to the preset value, the change-over signal into the pressurizing process is transmitted to work the pressurizing means 41. Then, a piston 44 pushes up the whole device of ball screw to execute the feeder head action to the molten metal in the cavity.