A flat fluorescent lamp is provided. Wherein, a discharge gas is disposed in a chamber, and a fluorescent material is disposed on a first inner wall and a second inner wall of the chamber. First electrode sets are disposed on the first inner wall, and second electrode sets aligned with the first electrodes sets are disposed on the second inner wall. A dielectric layer overlies the electrode sets. Each first electrode set comprises two first electrodes and a second electrode disposed between these first electrodes. Each second electrode set comprises two third electrodes and a fourth electrode disposed between these third electrodes. A first light-emitting area and a second light-emitting area are formed in each pair of the corresponding first and second electrode sets, and the projections of the first and second light-emitting areas on the first inner wall are not overlaid or just partially overlaid.