To provide a task ambient illumination system that secures an appropriate illumination environment and saves the energy of the illumination system.

Ambient illumination 11 are installed in rows at proper intervals inside a ceiling above an illumination region, multiple suspending tools 12 are fixed at proper intervals between the lines of the ambient illumination, power feeding rails 16 are suspended and fixed between the suspending tools generally parallel with a ceiling slab surface 10, supporting frame members 14 positioned generally parallel with and below the power feeding rails 16 are suspended and fixed between the suspending tools, louver units 17 having grid boxes 17b all over their surfaces or light transmission material units 20 are movably mounted between the supporting frame members 14 in parallel with one another, and task illumination 18 are transferrably mounted along illumination regions T between the louver units 17 and the light transmission material units 20.