PURPOSE: To obtain a method for executing surface heat treatment to a rod- shaped longitudinally extended material having metallic surface and an apparatus therefor by using rotary arc driven with magnetism around the axis of a strand.

CONSTITUTION: The arc 1 is shifted between a ring-electrode (anode) 2 and a strand 8 penetrating this electrode and utilized as an cathode. The problem in the development etc., of an improving method for stabilizing the arc, is resolved, by which the arc 1 rotates with a DC magnet 3 arranged in the strand passing direction at the back of the ring-electrode 2 and at the same time, the magnetic field induced with the DC magnet 3 reacts to the following effect of an arc leg point with the shifting strand and further, the ring-electrode current is divided into two partial currents. Particularly, the application field of this method is the surface heat treatment to the rod-shaped longitudinally extended material having metallic surface.