To provide a flat panel display device enabling a thin and lightweight configuration.

The flat panel display device comprises a display means for receiving supply of light for displaying a predetermined image, a light guide means having a supporting groove caved inward in one plane for guiding the light to the display means side, a luminance improving means for improving the luminance characteristics of the light guided by the light guide means, a storage means having a storage space including a bottom surface and four side walls for storing the light guide means and the luminance improving means and also having one or more first supporting members projecting from the side walls to the light guide means side so that they are coupled with the supporting groove for fixing the light guide means at a storage position on at least one of the four side walls, and a fixing means including a second supporting member corresponding to the first supporting member so as to be coupled with the supporting groove together with the first supporting member for fixing the storage position of the light guide means for fixing the light guide means and the luminance improving means.