PURPOSE: To easily manufacture a cast-in casting of a complicated shape by applying a substance which foams by heating to the surface of a ceramics semi-hard product, installing it in a mold and bringing it to cast-in by a molten metal.

CONSTITUTION: As for a substance applied to the surface of a ceramics semi- hard product, inorganic foaming substances of alkali silicate, alkali silicon zirconate, alkali aluminate, etc., of soda siliconate of a noncombustible foaming substance, etc., and one kind or two kinds or more thereof are used together suitably. In this state, the surface of the ceramics semi-hard product is coated with the material and set to a mold, and a molten metal is cast into a clearance between the mold and the applied layer. As a result, as soon as the foaming substance comes into contact with the molten metal, it foams and a foaming layer is formed between ceramics and the metal, and the generation of a fissure and a crack, and a defect, etc., are prevented.