To correct the deflecting direction of an arc by a method wherein a york is arranged so that its end forming parts face each other across an arc generating part and a current wire is wound around the york like a coil to form an arc deflection correcting magnet.

When a large current flows between a furnace bottom electrode 11 and a furnace top electrode 12 from a direct current power supply 14, a magnetic field acts on an arc generating region 26 and an arc 13 is affected by a force 32 having a direction in which the arc 13 tends to leave away from the direct current power supply 14. Therefore, a part of a current wire 15 on the furnace bottom electrode 11 side is wound around a horizontal connecting part 20 of a york 21 like a coil to form an arc deflection correcting magnet 31 and generate a magnetic field between a york end forming parts 23 and 24 in the opposite direction. Thereby, a force having a direction opposite to that of the force 32 that causes the arc 13 to deflect is generated and the deflection of the arc 13 is restrained. Therefore, local damages on the furnace wall due to the deflection of the arc 13 can be prevented.