An illumination optical apparatus illuminates a pattern on a mask with illumination light. The illumination optical apparatus includes an optical integrator, a polarization member arranged in an optical path of the illumination light on an incidence side of the optical integrator, which changes a polarization state of the illumination light, and a distribution changing member arranged in the optical path between the polarization member and the optical integrator, which can change a light amount distribution of the illumination light on a pupil plane of the illumination optical apparatus. The polarization member changes the polarization state of the illumination light so that a polarization direction of the illumination light, which is distributed away from an optical axis of the illumination optical apparatus on the pupil plane, is substantially coincident with a circumferential direction about the optical axis on the pupil plane.