PURPOSE: To perform titled welding uniformly and surely, by mounting a mouthpiece having mouthpiece pins to the end part of a tubular bulb and cutting the end parts of the mouthpiece pins together with the lead wires inserted therein and subjecting the same to arc discharge welding.

CONSTITUTION: A mouthpiece 2 fixed with mouthpiece pins 3, 4 is mounted in the end part of a fluorescent tube 1 while lead wires 5 for filament coils are held inserted in the pins 3, 4. In order to facilitate mounting of the mouthpiece 2 to the tube 1, the wires 5 are projected sufficiently longer than the end faces 31 of the pins 3, 4. The pins 3, 4 and the wires 5 are cut simultaneouly with a cutter along the line A-A' which is slightly inner than the end faces 31. After the tube 1 is slightly moved, electrodes 11, 12 are brought near the pins 3, 4 and the wires 5 to weld the pins and wires by arc discharge.