To achieve intentionally easier withdrawal of a CO gas generated from a granule layer during the reduction melting by enabling charging of a granular material during the operation as well to realize submerged arc electric melting which always enables generating of a foaming slag.

There are arranged one mobile negative electrode rod 6 and furnace bottom positive electrode bodies 8 buried so as to spread in the furnace bottom made of a carbonic refractory 7. Side charge ports 12 for forcing material 2 toward the mobile negative electrode rod 6 from the side of a furnace on to a foaming slag layer 11 formed to cover a molten slag 4 are installed at two or three points of a furnace wall at an equal angle within a surface at the same height positions. A pusher 15 for pushing out the material 2 from the side charge ports 12 supplies the material with the quantity thereof adjusted according to the height of a layer into the furnace with a rotary feeder 19. The thickness of the layer of the material pushed out is intentionally reduced gently to achieve easier withdrawal of a CO gas or the like from a thin layer part through which the material fails to spread.