To quickly remove a ceramic mold without remaining it in a hollow part and a complicated shape part in a casting, to improve the productivity and to increase the degree of freedom of the cast product shape by impregnating moisture in the ceramic mold stuck to the cast product, freezing the moisture and embrittling the ceramic mold.

The ceramic mold 2 for shell mold is dipped into the water together with the cast product 1, and when the temp. of the cast product 1 is lowered to almost room temp., this is pulled up and shifted to a steel-made vessel 4 and liquefied nitrogen LN is poured until the ceramic mold 2 is sufficiently dipped. When the boiling of the liquefied nitrogen LN is completed, the ceramic mold 2 is taken out from the steel-made vessel 4 and naturally cooled or heated to defrost the freezed moisture. After defrosting, the vibration and the shock are applied with a knock-out machine, etc., or the high pressure water jet WJ is applied onto the cast product 1 with a high pressure washing device 5 to remove the ceramic mold 2 from the cast product 1. The ceramic mold 2 is collapsed and falls down from the cast product 1 with the freezing expansion of the moisture and the shrinkage by cooling (-196°C) the cast product 1 or by defrosting.