An illumination unit of the present invention includes: an ellipsoidal reflector having a first focus and a second focus; an arc tube; a collimating lens; a first lens array 120 having a plurality of small lenses 122 for splitting the illumination luminous flux from the collimating lens into a plurality of partial luminous fluxes; a second lens array having a plurality of small lenses corresponding to the plurality of the small lenses 122 of the first lens array 120; and a superimposing lens for superimposing respective partial luminous fluxes from the second lens array at the illuminated area, characterized in that the light incident surface of the first lens array 120 is situated at the position which is closer to the ellipsoidal reflector than the second focus, and which is such that the light quantity of the illumination luminous flux from the collimating lens is distributed throughout over the light incident surface. This enables the achievement of the simplification of manufacturing processing and the reduction of the manufacturing cost of the first lens array without reducing the inplane light intensity distribution characteristics on the image formation area of the electrooptic modulation unit which is the illuminated area.