To provide a clean draft which has a simple constitution and is arranged in a room and in which scientific instruments and materials can be used.

The clean draft, which is used instead of the conventional clean draft arranged in the room for using scientific instruments and materials, is provided with: a rack by which the downside of a working space for housing scientific instruments and materials is covered and which has a substructure for forming a working plane; a hood by which the side parts and upper part of the working space are covered and which has an opening for communicating the working space with the room on the side surface; duplex doors by each of which the opening can be closed or opened and between which a space is interposed; an air intake pipeline system for guiding an indoor atmosphere into the working space; a first discharge pipeline system for discharging the gas in the working space; and a second discharge pipeline system for discharging the gas in the space between the duplex doors.