To prevent occurrence of casting defect by making the gas permeability on cavity sides of a mold larger than that of the proximity of a runner and gate parts, controlling pressure reducing degree as necessory and executing low speed introducing and high speed filling-up of molten metal, at the time of a reduced pressure suction casting by using the mold hanging down a refractory dome from the upper and of the runner.

At the time of executing the suction casting by arranging the mold 1 hanging down the refractory dome 13 in a mold housing chamber 5 communicated with a pressure reducing device 16, the product cavity 14 sides of the mold 1 are made of a ceramic mold 9 and the gas permeability thereof is larger than that of the proximity of the runner 11 and the gate parts 12. Further, if needed, the pressure reducing device 16 is used and the molten metal 4 from a holding furnace 3 is introduced to the proximity of a molten metal introducing part 8 or the runner 11 at the low speed. Successively, the pressure reducing degree in the mold housing chamber 5 is controlled so as to be filled up at the high speed to the product cavities 14 from the above part. Then, the adjustment of the gas permeability of the mold 1 can be achieved by applying refractory coating agent 10 all over the part from the runner 11 to the product cavities.