PURPOSE: To obtain a sound aluminum casting without casting defect of blow hole, etc., by arranging a gas venting pipe abutting on a porous ceramic surface at the position in a mold where the gas venting pipe is worked and removed after casting.

CONSTITUTION: The porous ceramic 2a is fixed in contact with a core 4a in the mold 1a and a gas venting pipe 3a abutting on the surface of the porous ceramic 2a is arranged at the position in a mold where the gas venting pipe is worked and removed after casting. Thereafter, molten aluminum alloy is poured into a cavity in the mold. Gas having tendency of remaining between the aluminum alloy and the porous ceramic is exhausted to the outside of the aluminum alloy through the gas venting pipe 3a. By this method, the sound aluminum alloy casting without the casting defect of blow hole, etc., is obtd.