To provide a casting apparatus which has excellent performance for discharging the inner pressure developed in a closed space communicating with a cavity to the outside in before starting the pressure-reduction in the cavity after mating a plurality of molds.

This casting apparatus 1 is provided with the mold which is constituted of a plurality of molds and formed of the cavity 13 on the mold mating surfaces thereof, and a pressure-reduction means 2 which fills up molten metal 16 into the cavity 13 by reducing the pressure in the cavity 13 through pressure-reducing piping 7. An inner pressure discharging means 17 for discharging the inner pressure developed in the closed space with heat-expansion of gas existing in the closed space communicating with the cavity 13 and new gas generated in the closed space before starting the pressure-reduction in the cavity 13 after mating the plurality of molds, is arranged in the pressure- reducing piping 7 or the cavity 13.