PURPOSE: To achieve required surface processing, and facilitate manufacturing by surface processing an external lead wire by hydrogen flames or hydroxide flames after sealing light emission filaments for removing a borate layer, replacing it by an inactive gas atmosphere, and cooling it.

CONSTITUTION: For a bulb after sealing a mount member and preheating an external lead wire by intermittent rotation of a rotary automatic transfer mechanism and reaching a reducer/cooler 6, a borate layer on the surface of the external lead wire is heated and reduced by hydrogen flames 6e fro a hydrogen gas flow nozzle 6b first to be removed. Next, high pressure inactive gas is blown from an inert gas blow nozzle 6c at a predetermined timing. As hydrogen gas in the reducer/cooler 6 is replaced by inert gas, the flames 6e are extinguished, and the external lead wire is cooled without being oxidized. A surface process can thus be achieved without crossing or entanglement of the external lead wire by curving or bending.