PURPOSE: To inexpensively and easily remove a thickly segregated part and slag by discharging the thickly segretated molten steel and slag remaining in the head part of a steel ingot during solidification.

CONSTITUTION: The thickly segregated molten steel 10 and molten slag 12 remaining in the head part of the solidified steel ingot 8 are discharged into a ladle 18, etc., by the removal, etc., of a top end 4A on one side of a casting mold 4 upon elapsing of the prescribed solidification time of the molten metal in the casting mold 4. The outflow is executed by constituting part of the casting mold 4 as a vertically movably casting mold or providing an outflow port closed by refractories at a suitable height of the casting mold and boring the outflow port, etc. The outflow may be otherwise executed by tilting the casting mold.