PURPOSE: To prevent oxidation of molten metal surface without bringing the molten metal into contact with the air by weighing molten metal flowed by molten piping under inert gas atmosphere and supplying it into a die.

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 a gas pressure room 2. The molten metal 3 is flowed in the gas pressure room 2 flowed in the weighing vessel recessed part 12a in an inner part cylinder constituent body 12, which is set to the necessary molten metal quantity, and an upper face of weighing piston 14. The selector valve 30 is made to connect through with the gas pressure room 2 through the gas cylinder 31, reducing valve 32 and gas supply/exhaust pipe 2b, to pressurize the upper part of the molten metal surface 3A in the gas pressure room 2. The inner part cylinder constituent 12 is ascended and the weighing piston 14 is ascended and the molten metal 3 weighed at the space between the weighing vessel recessed part 12a and the upper face of the weighing piston 14, is pressed in the die 20.