To use a bay window unit for multipurpose without losing natural lighting by disposing a housing part, an air-conditioner, an illuminator, a rolling screen and the like on both side parts and upper and lower parts of the bay window unit having a window part on the front face.

The sliding screen of an existing window is removed, and an eaves remains to attach a bay window unit on an opening part. Double sliding windows 41, 41 are provided on the front face of the bay window, the housing shelf 8 of cosmetic and the like having a single swing cover body 31 attaching a mirror on the rear, an air-conditioner for window attaching, a receptacle 34, and small windows for natural lighting 35, 36 are provided on both the side parts, a housing 23 having a cover body 24 with a knob in the same plane as a window board 22 is provided on the lower part, an illuminating instrument 13, a pipe for hanging a hanger 14 and a roll screen 15 are provided on the upper part. Thus, natural lighting is held as the bay window, a bay window is used for a dresser, an article housing and an airconditioner disposing, and the bay window can be used for multi-purpose for a closet and a washing article drying by partitioning the bay window space and the indoor space by a roll screen 15.