PURPOSE: To perform automatically welding with high accuracy without the possibility of giving any adverse influence of welding on others by branching a laser beam to the same number as the number of plural blank material of quartz or the like, irradiating the same to the joining surfaces of said materials to be melt joined to each other and controlling the lasers in such a way as to weld the joining surfaces to each other.

CONSTITUTION: An evacuation pipe G is set in a chuck 8b with both axial centers aligned to each other and a blank material E for a light transmission pipe is set in a chuck 8b with a small hole F and both axial centers aligned to each other, in the production of a light emitting pipe, for example, by welding the material E and the pipe G. The position of a driving member 20 and the diameter of a laser beam 26 from a device 25 are so adjusted and set that the beams 26a, 26b reflected by a mirror 19 are irradiated respectively to the periphery of the hole E and the end face of the pipe G. A control device 31 is then started to rotate both chucks in the same direction and at the same speed by a motor 11, thereby opening a shutter 27 and melting the joint surface parts. When the shutter 27 is closed and a linear moving device 22 is moved downward after a prescribed time, the mirror 19 moves downward and as movable bases 5a, 5b approach, the material E and the pipe G approach and the joining surfaces are joined by contact.