The present invention provides a flat panel display device and a stereoscopic display device. The flat panel display device includes a backlight system and a display panel. The backlight system includes a reflector plate and a back frame and the back frame carries the reflector plate. The back frame includes at least two primary assembling pieces, the at least two primary assembling pieces being joined to form a main frame structure of the back frame; and the reflector plate has a substrate containing a conductive fiber net for preventing electromagnetic interference. With the above arrangement, the lat panel display device and the stereoscopic display device of the present invention have a backlight system, which has a back frame having a simple structure, saves material for the back frame, and reduces the cost of the back frame. Further, the present invention integrates a conductive fiber net in a substrate of a reflector plate for preventing electromagnetic interference so that the flat panel display device and the stereoscopic display device that use a joined back frame of the present invention can achieve the purpose of preventing electromagnetic interference with an easy manner and thus further reduce the manufacturing cost of the flat panel display device and the stereoscopic display device.