To provide an illumination optical device forming a pupil intensity distribution of a desired shape and desired illumination and obtaining illumination conditions of great variety.

The illumination optical device has: a spatial light modulation unit composed of a first spatial light modulator 2 and a second spatial light modulator 3 arranged in the order of incidence of light; and distribution forming optical systems 5, 7 to form a prescribed light intensity distribution on an illumination pupil, based on luminous flux via the first spatial light modulator and the second spatial light modulator. The first spatial light modulator has a plurality of first optical elements 2a that are arranged two-dimensionally and are controlled individually. The second spatial light modulator has a plurality of second optical elements 3a that are arranged in correspondence to the plurality of first optical elements and are controlled individually.