In a load port portion of a conventional clean device, it can happen that cleanliness is reduced by dust caused by wear of bellows and a lid is not separated by its weight from a main body. In order to solve such problems, a clean device is structured as follows: a lid of a clean box has a non-circular reception hole, a load port portion of the clean device has an opening/closing mechanism with a projection fittable in the receiving hole and has a buffer chamber, one end of bellows of the buffer chamber is connected to the bottom surface of the buffer chamber, and the other end of the bellows is fixed, on the outside of the buffer chamber, to raising/lowering means of a port door.