On top of respective areas divided by partition plates, that is, a cassette station, a processing station, and an interface section in a coating and developing processing system, gas supply sections for supplying an inert gas into the respective areas are provided. Exhaust pipes for exhausting atmospheres in the respective areas are provided at the bottom of the respective areas. The atmospheres in the respective areas are maintained in a clean condition by supplying the inert gas not containing impurities such as oxygen and fine particles from the respective gas supply sections into the respective areas and exhausting the atmospheres in the respective areas from the exhaust pipes.