To provide an illumination optical apparatus, an exposure apparatus, and a device manufacturing method, that can contribute to higher output of a light source and improvement in manufacturing efficiency of a device even when spatial light modulation members are disposed in an optical path of light emitted from the light source.

The exposure apparatus 11 has the illumination optical apparatus 13 which guides exposure light EL emitted from an exposure light source 12 to a reticle R. The illumination optical apparatus 13 has a plurality of movable multi-mirrors 22 arranged in an array form, and each movable multi-mirror 22 is so configured that a plurality of reflecting optical element mirrors each including a movable reflecting surface are arranged in an array form. All the movable multi-mirrors 22 are arranged in an optical path of the light EL emitted from the exposure light source 12.