The present invention provides a flat panel display device. The flat panel display device includes a backlight system and a display panel, wherein: the backlight system includes a light source, a light homogenization mechanism, and a back frame; the back frame carries the light source and the light homogenization mechanism and the back frame includes at least first and second primary assembling pieces, in which the first primary assembling piece has an end forming at least two joint sections, and each of the joint sections has a structure mating an end of the second primary assembling piece. The back frame further includes a plurality of bracing pieces that are fixed to the primary assembling pieces. The bracing pieces include adjustable bumps mounted thereon and the adjustable bumps provide various mounting structures. The present invention also provides a stereoscopic display device and a plasma display device. The present invention has a mold for back frame that is of a simple structure, reduces the expenditure of the back frame mold, and also saves the material used for back frame so as to lower down the cost. Further, the bracing piece includes an adjustable bump mounted thereon to provide various mounting structures.