A load port is provided with a table and a plate. The table is arranged on a side of a front wall of an atmospheric transfer unit for transferring a piece of material under processing and is adapted to mount on it a container with the piece of material received in the same. The plate serves to isolate an interior of the atmospheric transfer unit from an exterior of the atmospheric transfer unit. The load port includes an exhaust duct arranged on a rear side of the plate and a fan arranged in a lower extremity of the exhaust duct. By the exhaust duct and the fan, an internal atmosphere of the atmospheric transfer unit can be exhausted into the atmosphere.