To enhance the emission luminance of a capillary tube type fluorescent lamp by providing a large gap between phosphor particles in a phosphor coating film and increasing a coating quantity in a specific range.

This lamp is a fluorescent lamp which is provided with a transparent glass tube in which an enclosed gas containing mercury and a rare gas is filled, a phosphor layer containing phosphor particles provided in the surface of the inner wall of the transparent glass tube and a means for maintaining positive discharge in an enclosed gas, and the following conditions are set. (1) The tube diameter of a fluorescent lamp is not more than 3.6mm. (2) The phosphor coating quantity per unit area of a phosphor layer is in the range of 3 to 8mg/cm2. (3) A gap ratio (e) expressed by the following formula is 40 to 80%: e=(V1-Vp)/V1×100(%), where V1 is the volume of a phosphor layer and Vp is the volume of phosphor.