In a processing apparatus for performing a specified process on a target object at a predetermined process pressure, the apparatus includes an evacuable processing chamber having a gas exhaust port formed in a bottom portion thereof; a mounting table provided within the processing chamber for holding the target object; a pressure control valve connected to the gas exhaust port, the pressure control valve including a slide-type valve body for changing an area of an opening region of a valve port; and a gas exhaust system connected to the pressure control valve. The pressure control valve is eccentrically arranged such that a center axis of the mounting table lies within an opening region of the pressure control valve formed over a practical use region of a valve opening degree of the pressure control valve.