PURPOSE: To easily obtain an ingot having unidirectionally solidified structure with a simple operation and device by heating the inside wall surface of a channel-shaped casting mold to the temp. of the ingot to contact said surface or above.

CONSTITUTION: The inside wall surface of the channel-shaped open top type casting mold 1 of which the inside wall surface consists of refractories having the heat conductivity lower than the heat conductivity of a casting metal and of which the base has a grade from the beginning end of solidification toward terminal thereof it heated by a heating element 4, etc., contained in the mold 1 so that the temp. of the inside wall surface to contact a molten metal 2 is maintained always at the solidifying temp. of the casting metal or above. The formation of crystal nuclei does not take place on the surface of the mold 1 in contact with the unsolidified molten metal 2 and the solidification is progress almost exclusively by the movement of the boundary face between the ingot 5 and the molten metal 2. Heat flow is always directed in the longitudinal direction of the ingot 5, i.e., from the molten metal 2 toward the cooling part by the heating of the mold 1, by which the ingot 5 having the unidirectionally solidified structure is easily obtd.