PURPOSE: To reduce bends and to impove the quality of casting surfaces by placing a heat insulating material of low m. p. on the top surface part of a mold, further placing a molding board thereon and making an ingot.

CONSTITUTION: A low m. p. heat insulating material 2 is placed on the top surface of a mold 1, and further a molding board 3 is placed thereon. When molten metal is successively changed in this state, the surface of the molten metal M ascends successively, and radiation heat reflects on the silver white surface of the bottom surface of the material 2, whereby the heat insulation on a long sized material is accomplished surely. When the moten M is filled in the mold 1, the material 2 is melted by said molten metal M, and the molten metal M is directly and quickly heated by the molding board 3. Hence, a long sized ingot of good surface characteristics and free from any bend is made. Any material which is easy to melt, has a silver white color, and possesses a constant degree of heat resistance is usable for the material 2.