PURPOSE: To melt consumable electrodes uniformly, by disposing the respective consumable electrodes in such a way that nonconsumable auxiliary electrodes are located on both sides thereof, connecting the nonconsumable electrodes to electric power sources having differing phases from the electric power sources of the consumable electrode and conducting electricity to a slag surface from the auxiliary electrodes as necessary.

CONSTITUTION: Consumalbe electrodes 1 are first supplied by a driving part 8 to the molten slag 3 in a water cooled metallic mold 2 made of copper, and electric current is conducted between the electrodes 1 and a solidified electrode 6 by an electric power source 9 for melting to melt the electrodes 1 in the molten slag. When the melting of the electrodes 1 is not uniform, auxiliary electrodes 1' are moved downward by a driving part 11 for control to bring said electrodes into contact with the surface of the slag 3, then electric current is conducted between the electrodes 1' and the metal 6 with the power source 9. The melting currents of all phases in the slag 3 can thus be conducted equally, whereby the melting of the electrodes 1 is made uniform without producing oxide slag and the formation of the molten metal bath 5 in the slag 3 is improved.