An illumination unit, comprising: an ellipsoidal reflector having a first focus (F 1) and a second focus (F 2); an arc tube having a light emitting portion in the vicinity of the first focus; a collimating lens for converting a light from the ellipsoidal reflector into a roughly parallel illumination luminous flux; a first lens array having a plurality of small lenses 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 of the first lens array; and a superimposing lens for superimposing respective partial luminous fluxes from the second lens array at the illuminated area, wherein the light incident surface of the first lens array is situated at a 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; characterized in that: a light incident surface of the collimating lens is situated at a position which is such that a dark area is present at the central part of the light incident surface of the collimating lens, the dark area not receiving luminous fluxes emitted from the first focus (F 1) and reflected by the ellipsoidal reflector, and the position at which the light incident surface of the first lens array is situated is such that the dark area is not present at the central part of the light incident surface of the first lens array, and the light incident surface of the first lens array is situated between the second focus (F 2) and a position at which light rays approaching from positions different from the first focus (F 1) and on the boundary of the dark area cross each other. an ellipsoidal reflector having a first focus (F 1) and a second focus (F 2); an arc tube having a light emitting portion in the vicinity of the first focus; a collimating lens for converting a light from the ellipsoidal reflector into a roughly parallel illumination luminous flux; a first lens array having a plurality of small lenses 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 of the first lens array; and a superimposing lens for superimposing respective partial luminous fluxes from the second lens array at the illuminated area, wherein the light incident surface of the first lens array is situated at a 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; a light incident surface of the collimating lens is situated at a position which is such that a dark area is present at the central part of the light incident surface of the collimating lens, the dark area not receiving luminous fluxes emitted from the first focus (F 1) and reflected by the ellipsoidal reflector, and the position at which the light incident surface of the first lens array is situated is such that the dark area is not present at the central part of the light incident surface of the first lens array, and the light incident surface of the first lens array is situated between the second focus (F 2) and a position at which light rays approaching from positions different from the first focus (F 1) and on the boundary of the dark area cross each other.