PURPOSE: To reduce preheating and cooling time and to perform titled casting efficiently by using double molding flasks, inside and outside, inserting and packing a backup material therein, and inserting a mold in the inside molding flask then preheating the flask, charging molten metal into the mold and removing the casting from the inside molding flask.

CONSTITUTION: A backup material 3 is packed between a cylindrical outside molding flask 1 of a square shape in section having a bottom flask 1' and an inside molding flask 5 erected on the flask 1', and bottom sand 6 is packed and installed in the inside bottom part of the flask 5. After a mold 2 is inserted in the flask 5 and set on the sand 6, a refractory cover 7 is inserted in the mold and is set on the flask 1. Therefore, the material 3 does not abut on the mold 2, and a spacing 8 is formed between the flask 5 and the mold 2. After the entire part is preheated in a preheating furnace, it is removed from the furnace, and while it has the heat insulating effect by the material 3, molten metal is charged into the mold 2, and in this state, the casting is cooled. Upon solidification, the casting is taken up from the inside of the flask 5, and the next mold 2 is reset in the flask 5.