To prevent the concentration of pores in the final solidified part of an aluminum alloy casting and to spherically micronize the pores by combining a stage of removing oxides from the molten metal of an aluminum alloy and a stage of executing inoculation to the molten metal and a stage of adding hydrogen to the molten metal.

An inert gas is blown in to the molten metal of an aluminum alloy to remove oxides. One or more kinds among Al-Ti alloys, Al-B alloys, Al-Ti-B alloys, Al-Ti-C alloys and flux contg. Ti and B are added to the Al alloy molten metal, and inoculation is executed. Hydrogen is added to the Al alloy molten metal by metallic hydrides. By the oxide removing stage, film shaped oxides causing the generation of coarse pores are removed away. By the inoculation, the crystalline grains are made fine, so that pores can be micronized. By the addition of hydrogen, shrinkage is relaxed and dispersed, and pores are made spherical. The A1 alloy casting usable for intake parts for automotive use requiring airtightness and strength can be obtd.