PURPOSE: To repeatedly supply molten metal having always higher than thee prescribed temp. into a die and to prevent oxidation without contacting with the air by supplying the molten metal in a gas pressure room into a weight supplying means by vertically moving the metal surface by controlling the pressure in the gas pressure room.

CONSTITUTION: A selector valve 30 is made to exhaust pressure side and gas cylinder 31 side is closed by the selector valve 30 and a gas supply/exhaust pipe 2b side is opened, to reduce the pressure of the inert gas at the upper part of the molten metal surface 3A in the gas pressure room 2. The molten metal 3 is flowed in the gas pressure room 2 and flowed in the weight vessel recessed part 12a in an inner part cylinder constituent body 12, which is set to the necessary molten metal quantity to the die 20, and an upper part of weighing piston 14. Next, the selector valve 30 is made to connect-through state with the gas pressure room through the gas cylinder 30, reducing value 32 and gas supply/exhaust pipe 2b to pressurize the upper part of the molten metal surface 3A in the gas pressure room 2. At the same time, the piston 13b is ascended and the inner cylinder constituent body 12 is ascended and the weighing piston 14 is ascended, to press the molten metal 3 in the die 20.