To provide a lighting optical device which can correct the variation in illuminance by a simple structure even if an illuminance distribution on a lighted surface changes with time.

The lighting optical system (1-11) lights an illumination region on the surface (M) to be lighted by a flux of light from a light source (1). It contains an optical integrator (9) for wavefront-dividing the flux of light from the light source by a plurality of wavefront division regions, and a correction filter (8) having a unit distribution region having a prescribed transmittance distribution. The correction filter is so structured as to be movable in a direction perpendicular to the optical axis (AX) to allow the flux of light passed through the unit distribution region to enter a region spread over at least two adjacent wavefront division regions out of the plurality of them.