An illumination device includes a light source unit; and a light guide plate configured to guide light from the light source unit and to emit the light outward. The light guide plate includes an incidence surface which constitutes one end surface of the light guide plate and on which the light from the light source unit is incident, and emission surfaces which constitute opposite main surfaces of the light guide plate and from which the light incident on the incidence surface is emitted. The emission surfaces include dots formed by micro prism processing. The dots on one of the emission surfaces and the dots on the other emission surface are position-shifted in rotational symmetry with each other.