A liquid crystal display device has a plurality of lamps, a light diffusion plate and/or an optical sheet, a shield portion for accommodating the lamps, the light diffusion plate and/or the optical sheet. There is a liquid crystal display panel located opposite to one side of the light diffusion plate and/or the optical sheet opposed each with the other side to the lamps. The light diffusion plate and/or the optical sheet each have a vent, and a lamp chamber formed in the lamp-accommodating side of the light diffusion plate and/or the optical sheet. There is an LCD panel chamber formed in the LCD panel-disposing side of the light diffusion plate and/or an optical sheet that communicate with each other through the vent of the light diffusion plate and/or optical sheet.