PURPOSE: To supply the desired quantity of molten metal in high precision of weighing by arranging a reverse U shaped tube between a molten metal basin part and a furnace, rising the furnace according to variation in the height of molten metal surface in the molten metal basin part and keeping the height of the molten metal surface to almost the constant in each shot.

CONSTITUTION: At the time of pressurizing a B chamber by working pressurizing gas supplying device 47, 48a, 48b, 49, the molten metal 15b in the B chamber is supplied into an A chamber through the inner part of the reverse U shaped tube 30, and the molten metal 15a reaches to a prescribed level while being detected with a molten metal surface sensor 24. By reading the values of the molten metal surface sensor 24 and a temp. sensor 25 into a servo moter control device, the setting data of the molten metal pouring quantity, etc., too, the starting signal of the molten metal pouring are waited. By the pouring command, the servo motor 26 is worked and the weighing valve rod 26 is risen and the molten metal 15a starts to flow into an injection sleeve 3. Ac-cording to the variation in the height of the molten metal 15a surface in the molten metal basin part 2, the furnace 1 and the molten metal 15b surface are risen to execute the molten metal supplying work so as to keep the height of the molten metal 15a surface to almost the constant at each time of pouring the molten metal.