Illumination optical assembly, exposure apparatus, and device manufacturing method

An illumination optical system can form a pupil intensity distribution with a desired beam profile. The illumination optical system for illuminating an illumination target surface with light from a light source is provided with a spatial light modulator which has a plurality of optical elements arrayed on a predetermined surface and individually controlled and which variably forms a light intensity distribution on an illumination pupil of the illumination optical system; a divergence angle providing member which is arranged in a conjugate space including a surface optically conjugate with the predetermined surface and which provides a divergence angle to an incident beam and emits the beam; and a polarizing member which is arranged at a position in the vicinity of the predetermined surface or in the conjugate space and which changes a polarization state of a partial beam of a propagating beam propagating in an optical path.