To provide a spatial light modulation unit capable of avoiding, in a reliable manner, optical members from being damaged by light excessively condensed through multiple mirror elements.

A spatial light modulation unit (3), used in an illumination optical system which illuminates a surface to be illuminated with light from a light source, comprises: multiple mirror elements (30a; SEa-SEd) arranged in a predetermined plane and controlled individually; a spatial light modulator (30) in which reflection surfaces of the multiple mirror elements are formed in concave (convex) shape; and light flux conversion element (31) which converts incident light flux into divergent luminous flux (or converging luminous flux ) and guides it to the spatial light modulator.