Disclosed is a flat fluorescent lamp, including a back substrate, a front substrate made of a transparent material and mounted on the back substrate through a sealing member disposed therebetween, a plurality of partitions disposed between the back and front substrates to define a discharge channel therebetween, a fluorescent material layer coated along a surface of the discharge channel defined by the partitions, a plurality of electrodes disposed to both the back substrate and the front substrate to cause a dielectric barrier discharge, and a reflective layer to cover the entire back substrate and upper portions of the electrodes disposed to the back substrate. In addition, a backlight unit is provided, including the above flat fluorescent lamp, a light diffusion part spaced from a top of the front substrate of the flat fluorescent lamp to diffuse light irradiated from the flat fluorescent lamp, an insulating layer disposed under the reflective layer of the flat fluorescent lamp through a first adhesive layer, and a base member disposed under the insulating layer through a second adhesive layer. Such a backlight unit is advantageous in improvement of uniform characteristics of luminance and supplement of durability of the lamp upon combination of the lamp and the base member.