A processing apparatus includes: a processing container having a substantially cylindrical shape; a gas nozzle extending in a longitudinal direction of the processing container along an inside of a side wall of the processing container; an exhaust body formed on the side wall on an opposite side of the processing container to face the processing gas nozzle; and an adjustment gas nozzle configured to eject a concentration adjustment gas toward a center of the processing container. The adjustment gas nozzle is provided within an angle range in which the exhaust body is formed at a central angle with reference to the center of the processing container in a plan view from the longitudinal direction.