A planar light source has a light emitting source, and a light guide plate for receiving light beams emitted from the light emitting source at a front side thereof and changing direction of the light beams, discharging the light beams from an upper surface thereof. A first anisotropic diffusion surface is formed on a lower surface of the light guide plate, and a reflection member is provided on the first anisotropic diffusion surface. The first anisotropic diffusion surface is a hologram diffusion surface or a hairline diffusion surface.