A wedge shaped lighting device includes a light source and a light guide plate disposed opposite to the light source, and the light guide plate includes a light entrance plane opposite to the light source and a light exit plane containing one side of the light entrance plane, and has a shape growing thicker in direction perpendicular to the light exit plane with the increasing distance from the light entrance plane and contains scattering particles for scattering light entering through the light entrance plane and propagating the inside thereof.