PURPOSE: To facilitate the repairing of an electrode and prevent the occurrence of the drift of current by a method wherein a steel cylinder, having a thickness of a specific range and a sectional area whose average current density is lower than a specific value, is connected to a supporting base plate at the lower side of a hearth electrode while the inside and outside sections of the steel cylinder are constituted of a refractory.

CONSTITUTION: A base plate 5 and a supporting base plate 6, which are provided in parallel to each other, are connected through coupling columns 10 while a flow regulating plate is formed on the base plate 5 in order to conduct cooling air, which flows into a furnace through a cooling air introducing passage 4a, effectively. A steel cylindrical electrode 12 is connected to the supporting plate 6 integrally and is formed so as to be a cylindrical hearth electrode having a sectional area having the thickness of 30-60mm and the average current density of 0.5A/mm2 or less. The width of groove is specified so as to be 30mm or more whereby the insertion of a steel cylinder for repairing is facilitated when the steel cylindrical electrode is consumed by operation for a long period of time and the upper end of the electrode becomes lower than a surrounding electrode block so as to generate a recessed groove type damage. On the other hand, the width of the groove is specified so as to be smaller than 60mm whereby the flow of molten steel is restrained while the average current density is specified so as to be 0.5A/mm2 whereby excessive Joule heat will never be generated.