PURPOSE: To manufacture at ordinary temp. in a short time a strong casting mold having fire resistance, excellent casting surface and dimensional accuracy, by filling the space made between a pattern plate and a die with sand contg. a prescribed ratio of fine particles, then by removing the pattern plate after curing of the sand.

CONSTITUTION: Sand for cold box process composed of 5W20wt% finely powdered sand of high purity under 200 meshes, the balance being relatively fine sand over 200 meshes, is prepared. Said sand for cold box process blended with a binder is blown into the spaces 4, 4' made between patterns 2, 2' having a pattern plate 1 and dies 3, 3', then it is cured by passing gas. The pattern 2, 2' are removed, and thin cold box shell molds 5, 5' backed with dies 3, 3' are obtained. The molds have about 900kg/cm2 strength, which is about two times that of usual mold for cold box process.