PURPOSE:To form a casting for a molding die for which various additive working stages are considerably reduced by bringing a master mold formed of porous ceramics and a die model formed of a combustible resin into tight contact with each other, embedding the same into mixed sand, pouring a molten metal therein to burn the model and venting gas from the outside circumferential part of the sand. CONSTITUTION:A master mold 10 formed of porous ceramics and a model 1 formed of a combustible resin into a die shape are brought into tight contact with each other on a molding surface 11 and are embedded into mixed sand 13. Plates 14, 15 having nozzles 16, 17 are disposed above and below the sand 13. A molten metal is charged through a riser gate 18 into the model 1 and at the same time the gas generated by the combustion of the model 1 is sucked through nozzles 16 by an evacuating pump. When the molten metal is filled up to the gate 18, the evacuating pump is changed over to such the gas through nozzles 17. The molten metal poured onto the master mold 10 is solidified and the evacuated condition is maintained until the additional molten metal is poured through the gate 18. The casting which can be made into a final product with the slight polishing alone is thus formed.