An illumination optical system comprises a first polarization control unit which is located between a light source and a pupil of an illumination optical system, and a second polarization control unit which is located between the first polarization control unit and the pupil, wherein a region on the pupil includes a plurality of partial regions which are classified into a first group including a partial region having a largest area, and a second group including a partial region different from the partial region having the largest area, and the second polarization control unit controls a polarization state in the partial region which belongs to only the second group.