PURPOSE: To prevent reverse V segregation in a steel ingot and to suppress formation of porosity by detecting the cavity owing to solidification formed in the steel ingot and the inside wall of a casting mold with the value indicated on a load cell and setting the min. value for the indicated value thereby controlling ingot making.

CONSTITUTION: The ratio at which the weight of a steel ingot is supported by a casting mold 8 is decreased on formation of a cavity and the value indicated on a load cell 4 increases. When the value indicated on the cell 4 exceeds a set value, the formation of the cavity is detected, and the pressing force on a long- side casting mold 14 by a pressing device 24 is decreased at this timing and a casting mold 18 on a short side is moved upward and at the same time, the device 24 for the mold 14 is actuated to move and press the mold 14 from the outside to the inside thereby eliminating the cavity formed in the steel ingot. Such operation is repeated until the steel ingot solidifies thoroughly to bring a water cooled copper plate 10A on the long side into contact with the surface of the steel ingot, by which the solidifying rate of the steel ingot is remarkably accelerated and the generation of reverse V segregation is prevented.