PURPOSE: To intend stabilized quality and enhanced yield in manufacturing fluorescent lamps by previously drying coating liquid on the inner face of a glass tube with hot air at a low temperature into a good condition without spots before proper dry efficiently with hot air at a high temperature.

CONSTITUTION: A low-temperature drying furnace 10 previously dries coating liquid on the inner face of a glass tube 3 little by little by giving downflow of hot air at 30-40°C. A high-temperature drying furnace 11 properly dries the coating liquid by blowing hot air at 40°C or more against the glass tube 3 in a tray 4 delivered from the low-temperature drying furnace 10. At this time, as the high-temperature drying furnace 11 is at a separated position from the low-temperature drying furnace 10, the glass tube 3 in which the coating liquid is previously well dried in a dry condition of being stable all times is delivered together with the tray 4 from the low-temperature drying furnace 10 to the high-temperature drying furnace 11. It is thus possible to dry the coating liquid uniformly over the total length of the glass tube and stabilize the quality of a fluorescent film which is formed later.