A flat type fluorescent lamp, obtaining an improvement in efficiency of brightness and being adjustable in an emitted light amount thereof, while maintaining a uniform light emission across the surface thereof, and illuminating with no use of mercury therein, comprising a sealed container being defined between a front glass substrate and a rear glass substrate which are hermetically bonded to each other, so as to enclose a rare gas as discharge gas therein, edge electrodes, having width from 2.5 mm to 10 mm and being provided at both end portions on one surface of the sealed container, and other edge electrodes, having width from 5 mm to 20 mm and being provided at both end portions on the other surface thereof, wherein the edge electrodes on the same side surfaces are connected to each other, a first inverter is connected between the one edge electrode P3 and a central electrode P6 which is provided in a central portion of the one surface, and a second inverter is connected between the other edge electrode P4 and the central electrode P6, wherein the first inverter and the second inverter provide rectangular waveform outputs, being same in frequency but having phases different to each other, thereby illuminating the lamp.