PURPOSE: To provide a titled robot for welding which recognizes a weld line by direct monitoring near a torch and guides exactly the torch by emitting laser light and detecting the light reflected from objects to be welded.

CONSTITUTION: A laser light source 13 makes swing motion around a fulcrum 12 integrally with a welding torch 4. The laser light advancing rectilinearly through a semitransparent mirror 14 according to said motion scans the region including the groove perpendicularly to the weld line. On the other hand the light reflected from objects 1 to be welded is partly reflected by the mirror 14 and is made incident to a laser light detector 15. The fluctuation in the position of the torch 4, the groove 2 and groove gap with respect to the weld line is known is accordance with the output waveform from a laser light detector 15. The position of the torch 4 is corrected by a means 16 for controlling the position of the torch in accordance with said fluctuation.