PURPOSE: To facilitate the adjustment at the top end position of a filler metal and to improve the weldability of a weld zone by inserting said metal from the direction coinciding with the optical axis of a lens which condenses laser light.

CONSTITUTION: Assist gas 6 is supplied from the spacing between an outside pipe 5 and an inside pipe 7 to the spacing 4 at the top end of a torch body 1 and is discharged along the inside wall of the space 4. Laser light 9 is condensed, via a lens 2, and is radiated to a material 11 to be welded; at the same time, a filler metal 8 is fed through the pipe 7. Since the top end of the pipe 7 coincides with the optical axis of the lens 2, the metal 8 coincides automatically with the optical axis of the lens 2 and there is no need for adjusting the position for inserting the metal 8. The light 9 to the pipe 7 is shielded by a reflection plate 10 and therefore the pipe 7 is cooled by cooling water and is kept free from damaging. The material 11 and the metal 8 are heated and melted by the light 9 and the metal 8 is fed at a prescribed speed, whereby welding is accomplished.