PURPOSE: To reduce the structural members, improve transportation efficiency of the structural members, and facilitate assembling at a construction site.

CONSTITUTION: A front side panel 12 is arranged opposite while keeping a luminaire arranging space 11 between it and a side wall panel 5 arranged along the side wall 1 of a building, and a luminaire installing member 13 is fixed to the side wall panel 5. Illuminating reflecting surfaces 15 and 16 are formed on the opposing surface between the side wall panel 5 and the front side panel 12. Thereby, the structural members can be reduced, and transportation efficiency of the structural members can be improved, and assembling can be also facilitated at a construction site.