To secure the wide moving area of an illumination lamp in the state of arranging an illumination device inside a shelf device and to effectively utilize the shelf device after detaching the shelf device for constituting a desk.

A middle shelf device 14 and an upper shelf device 15 are arranged on a top plate 12 and the illumination device 16 is supported by the middle shelf device 14. The illumination device 16 is constituted of a base 55 in an inclined posture rotatable within a horizontal plane, an arm 56 hinge- connected to the base 55 and the illumination lamp 57 provided on the tip side of the arm 56. Then, by adjusting the rotation position of the base 55 and the angle of the arm 56, the illumination lamp 57 is moved to the lower surface side position and front part position of a shelf plate 37 for an upper shelf and a position elevated or lowered from the respective positions. Also, for the middle shelf device 14, a shelf plate 29 for the middle shelf is detachable and a computer display 52 is arranged on the top plate 12 in the state of detaching the shelf plate 29 and the upper shelf device 15. Also, the detached upper shelf device 15 is connectable to a separate housing shelf 60.