PURPOSE: To reduce the output of laser beam with simple positioning process and enable extremely good welding by melting a location near the pedestral section of a thick section using laser beam and welding the pedestral section to a support section indirectly so that the molten part can be made to flow on the pedestral section.

CONSTITUTION: A cathode sleeve 22 provided with a base metal 21 fitted and fixed at its top is imbedded in the insulating support rod of an electron gun. After a coil section 23 is wound in a double helical form in this cathode sleeve 22, a heater 25 consisting of said coil section 23 coated with an insulation member and a pedestral section 24 not coated with the insulation member permits said pedestral section 24 to be welded to the tab 27 of almost U-shaped support rod 26 at a welding point 28. After this support body 26 positions the coil section 23 in an imbedding piece 29 for the support body imbedded in the insulating support rod and the cathode sleeve 22, it is fixed at a welding point 30 and then a section 261 is removed. A thick section 27a is formed at the opposed section of the tab 27 and this thick section 27a is used as the guide section of the pedestral section 24. Simultaneously, a location near the pedestral section 24 of the thick section 27a is melted by shooting laser light 31 and the pedestral section 24 and the tab 27 are welded together indirectly by means of this melted member 26a1.