An illumination device is provided and has a light guide plate, a light source and a light modulator, wherein the light modulator has a pair of transparent substrates a pair of electrodes and a light modulator layer. The light modulator layer includes a first region being changed between a transparent state and a scatterable state depending on intensity of an electric field, and a second region being more transparent than the first region in a scatterable state at an electric field having a certain intensity, the electric field being applied when the first region is changed between the transparent state and the scatterable state, and an occupancy rate of the first region in the light modulator layer is increased with increase in distance from the light source.