A low-pressure casting apparatus that prevents molten metal that is a residue in a conduit from being oxidized. The low-pressure casting apparatus includes a compartment for holding a molten metal 1, a pressure chamber 2 that can communicate with the compartment, wherein the molten meal is pressurized in the chamber, an on-off valve 5 that opens and closes hole 4 through which the compartment can communicate with the pressure chamber, a conduit 7 that conducts the molten metal to the mold 6, wherein the base of the conduit is connected to a lower part of the chamber so as to communicate with the chamber, the end of the conduit being made so that it can communicate with a sprue for a mold 6, a float 9 that goes up and down in the pressure chamber, and a tank that stores an inert gas and that has a pipe 13 that is connected to the upper part of the pressure chamber 2. The base of the conduit is connected to the pressure chamber so that the conduit can communicate with a space that is formed above the molten metal in the pressure chamber, when the level of the molten metal is lowered by raising the float after the molten metal in the mold has solidified, the mold having been filled with the molten metal by lowering and immersing the float in it which causes the level of the metal to rise.