To provide a protective device for saving and reducing electric power consumption to one part in several by using an air conditioner or the like in a divided cell formed by a dividing body for restricting a capacity of an ordinary room to one part in several.

A divided cell and a remaining cell are formed by dividing a capacity of the room to one part in several so as to surround a wall on a window side on which the air conditioner or the like is installed. A dividing body comprises a dividing material which can be easily folded for generally restoring the original room when no in use, and an inhibiting material for generally inhibiting flowing of air between the divided cell and the remaining cell by reducing gaps between a periphery of the dividing material and a ceiling/ floor/sidewall. Thereby, while the room such as a large hall, a private room, or the like is used as a small room by dividing into the cell having the capacity of one part in several of the original room, power consumption of the air conditioner or the like is reduced generally to one part in several, and the original room can be restored easily as necessary.