PURPOSE: To prevent unburnt gas from being blown out of an electrical furnace by a method wherein air is fed into an electrical furnace to a downward part of a central part of a discharged gas feeding duct from at least two air nozzles and the unburnt discharged gas generated within the electrical furnace is burned in second combustion near a lower part of the discharged gas feeding duct.

CONSTITUTION: Heat energy of discharged gas generated within an electrical furnace 1 is fed to a scrap preheating tank 5 through a discharged gas feeding duct 4 arranged at an upper lid 1a of the electrical furnace 1 and applied for a pre-heating of scrap 12 stored there. A secondary combustion is carried out near a lower part of the discharged gas feeding duct 4 by feeding air from two to four air nozzles 8 through the air feeding pipe 7 under an operation of a blower 6 toward a part near the discharged gas feeding duct 4. Accordingly, the unburnt discharged gas generated in the electrical furnace 1 is not blown out of the discharged gas feeding duct 4. Due to this fact, a facility for burning unburnt discharged gas other than the electrical furnace 1 can be eliminated.