An illumination device according to the present invention includes: a light source row in which a plurality of light sources are aligned in a row; a light guide plate that includes a plate-shaped main body with an end thereof facing the light source row, a light-receiving portion that is arranged on the end of the main body and into which light from the light sources enters, plate-shaped side extensions that are arranged on the sides of the main body and that extend outwards further than the light-receiving portion, and a light-exiting portion that is arranged on front surfaces of the main body and the side extensions and that allows light that enters via the light-receiving portion to exit; and a supply unit that supplies light to the side extensions.