PURPOSE: To quicken the solidification of the thick part of a casting and prevent the occurrence of casting defect such as casting blow hole in this part by locally quenching the thick forming part in a core at super low temp. with liquefied nitrogen and using this core to execute the casting.

CONSTITUTION: Before setting the core 1 into a master mold, the liquefied nitrogen 5 is blown toward the thick forming part 2 through a nozzle having 4mm inner diameter from the position where the tip part of the nozzle 4 is apart from the surface of the core 1 by the distance L=20-30mm to locally cool and thereafter, the core 1 is immediately set in the master mold to pour the molten metal. By this method, the sound casting 3 without occurring the casting defect such as the casting blow hole is obtd. in the thick part. Further, since any chiller is not used, the trouble of setting, removal, recovery, etc., of the core can be eliminated.