PURPOSE: To supply the molten metal in a static flow and to stabilize the quality of the molten metal without stopping the casting machine when the molten metal is supplied, without any problem of sealability, without any remarkable fluctuation of the surface of the molten metal at the molten metal holding part, and without complicated control of the air pressure.

CONSTITUTION: A molten metal holding part 11 of a low pressure casting machine 10 is connected to a molten metal holding furnace 40 by a piping 25 at the position lower than the surface of the general molten metal of the molten metal holding part, and an opening/closing valve device 30 to switch the flow of the molten metal into the piping and the stop is provided in the piping within the molten metal holding furnace.