To provide an illumination device in which a point light source and a reflective member based on a light weight, cheap resin material is used, the illumination device has high precision and is strong to environmental variations when in a state assembled as a unit and is easily moldable as a part, a plurality of point light sources (111) is arrayed, a first reflective member (112b, 112c, 112d) is disposed along an outgoing direction of light of the point light sources, a second reflective member (112e) is disposed in a surface opposed to a light emitting surface of the point light source in an orthogonal direction, the point light sources are moved integrally with a part or a whole of the first and the second reflective member, the illumination device irradiates an irradiation surface by light from the point light sources, rib shaped bodies (112a) are disposed in a light passageway side of the first reflective member, the rib shaped bodies includes a reflective surface and is situated at a position of an approximately equal distance from two adjacent point light sources, the rib shaped bodies are disposed to be approximately orthogonal against a straight line connecting the two adjacent point light sources.