PURPOSE: To secure the degree of vacuum inside a curved tube type fluorescent lamp and improve the characteristics of the lamp, by setting the ratio of the inside diameter of a curved tube type bulb to the inside diameter of an exhaust pipe within a predetermined range.

CONSTITUTION: In a curved tube type fluorescent lamp curved into a saddle-like shape, the ratio of the inside diameter dB of the bulb 18, to the inside diameter dE of an exhaust pipe 23 communirated to the inside of a curved tube type bulb 18, that is, dE/dB, is set within the range of 13W30%. Thus, the degree of vacuum equal to a general straight tube type or circular fluorescent lamp can be secured without using any particulary large exhaust device in spite of large conductance at the time of substituting gas in the bulb 18. Thereby, the characteristics of the lamp can be improved without any bad effect to a lumen maintenance factor, the starting characteristics of the like.