PURPOSE: To eliminate occurrences of unmolten residues at the end of bevelings and, at the same time, to improve both quality and efficiency of welding, by changing the amplitude and phase of the nonconsumable electrode and filler metal, when both are weaved in the same period.

CONSTITUTION: A fixing base 18 provided with a wire guide table 17 is fixed to a torch mount 10 which welds a material to be welded 1 at a beveling 2. Moreover, a sliding bearing 13 provided with a wire fixing table 16 is mounted on the fixing base 18 so that the bearing 13 slides freely in the direction normal to the axis of torch and horizontally, and a sliding base 9 is fixed to it. The location of a filler metal 6 is adjusted in the direction of depth of beveling, by turning a knob 14 of the base 9. A weaver 12 oscillates a torch 3, i.e. an electrode 4, through a shaft 11, and the movement of the shaft 11 changes the amplitude and phase through transmission shafts 19 and 20 and an eccentric cam and oscillates the bearing 13, i.e., the base 9, with a oscillating wire 15 fixed to the table 16. Therefore, the filler metal 6 is oscillated irrespective of the electrode 4, and, the locus of them and an arc 7 becomes that the amplitude of 6 is larger than of 4. Moreover, when the electrode 4 is at the center of beveling, the filler metal 6 is outside of the electrode 4.