To solve the problems of deterioration in display image quality of the air cooling system of a flat panel display device caused by foreign substances which are dust and soot or the like included in the air being sucked in as heat carrying medium and are adhered and accumulated on the surfaces of internal optical parts such as a display panel, a light diffusing plate and light reflecting plate or the like over a long period of time while the apparatus is used.

A cooling air path 15 is formed at a main frame which is a supporting structure commonly used as a heat sink and a back cabinet to be spatially isolated from other electronic circuit parts and optical parts in the casing of the apparatus. Moreover, the electric circuit parts which are heat generating sources are abutted on the main frame via a heat conducting material to efficiently conduct generated heat from the electronic circuit parts to the main frame and to exhibit the cooling effect.