PURPOSE: To obtain an optical compensation type STN liquid crystal display device with high brightness and contrast more than ever by specifying the refractive index in the thickness direction of a transmissible sheet.

CONSTITUTION: Phase difference plates 2 are arranged at the upper and lower sides of a liquid crystal panel 11, and polarizing plates 3 at the upper and lower sides of them, and the transmissible sheet 4 is arranged at the lower side, and a diffusion plate 5 and a fluorescent lamp 6 are arranged at the lower side of the sheet 4. The refractive index in the thickness direction of the transmissible sheet 4 is formed larger than that in a perpendicular direction. Light from the fluorescent lamp 6 that is a light source can be made incident first on the liquid crystal panel 11 and the phase difference plate 2 perpendicularly as much as possible. In other words, the light from the fluorescent lamp 6 is made incident on the transmissible sheet 14 whose refractive index in the thickness direction is larger than that in the perpendicular direction, and the perpendicular component even of diagonal light can be increased. Therefore, light compensation can be applied comparatively ideally, which intensifies the contrast.