PURPOSE: To make bead shapes at the weld start end even by making the wire feed speed up to the arc start position lower than steady speed and controlling the torch moving speed after detection of arc higher than the steady speed.

CONSTITUTION: The bottom in the groove is beforehand ground with a grinder. A welding truck 9 is run at a steady speed and at the same time a wire 1 is fed at a low speed by a wire feed motor 4. Along with running of the truck 9, the output signal of a torch position detector 5 is inputted to a control unit 8. In detecting the arc start position b, the wire 1 is gradually fed to the weld base metal face 10 and the point where the wire 1 and base metal 10 contact and current flows in the wire 1 is detected with a shunt 13. The output of the position detector 5 of that time is stored in the control unit 8. During the time from the arc detection until the wire feed speed becomes steady, the truck running speed is controlled to a speed higher than the steady one, whereby the quantity of deposition is reduced and the adequate start end bead is obtained.