PURPOSE: To prevent oxidation wearing of a wearing electrode by successively connecting a graphite-based wearing electrode covered with SiC film to the bottom of a non-wearing electrode.

CONSTITUTION: A composite electrode 1 comprises a wearing electrode 3 coated with an SiC film 5 and a non-wearing electrode 2. The electrode 2 connected to the electrode 3 via a graphite nipple 4, when worn by a refining work, is replaced with a new electrode to continue the refining work. As the wearing electrode 3, a graphite electrode with the side thereof formed with an SiC film is used and the end surface thereof provided with a thread portion for a nipple connection connected to the wearing electrode via the nipple. As a result, a considerable reduction in the unit requirement in the refining work is possible.