PURPOSE: To prevent the generation of casting defects such as shrinkage cavity arising from the defective heat insulation of a metallic mold by providing plural hermetic chambers to the metallic mold and adjusting respectively the degree of vacuum in the respective hermetic chambers thereby controlling the solidification of the molten metal in a cavity.

CONSTITUTION: The metallic mold 1 is formed of a cope 2, a horizontal mold 3 and a drag 4. The hermetic chamber A is formed to the cope 2, the hermetic chambers BWE are formed to the mold 3 and the hermetic chamber F is formed to the drag 4. After the mold 1 is closed, the inside of the chambers AWF is evacuated via a vacuum pump 7. The degree of vacuum in the chambers A, B is made approximately the same and the degree of vacuum is made gradually larger from the chamber C toward the chamber E; the degree of vacuum in the chamber F is made about the same as the degree of vacuum in the chamber E. The degree of vacuum for the thin-walled part is smaller than the degree of vacuum for the thick-walled part and therefore the solidification of a molten metal in the thin-walled part is retarded when the molten metal is filled into the product cavity 5 in this state. The product having no casting defects is thus obtd.