An annulus fluorescent lamp comprises a plurality of annulus fluorescent tubes having different diameters and disposed substantially concentrically in substantially the same plane. Each of the annulus fluorescent tubes has a first end with electrodes and a second end without electrodes. The second ends of the annulus fluorescent tubes are communicated with each other via a bridge portion so that a single discharge path is formed inside the plurality of annulus fluorescent tubes. The annulus fluorescent lamp also comprises a mouthpiece covering the first and second ends of the annulus fluorescent tubes. The second end forms the lowest temperature portion. The mouthpiece is provided with through holes for ventilation close to the second end and an insulating wall on an inner face for separating power lines at the first ends from the through holes for ventilation.
