Apparatus for reduced-pressure epitaxial growth and method of controlling the apparatus

An apparatus for reduced-pressure epitaxial growth comprising a processing furnace, a susceptor disposed in the processing furnace and rotates while placing a semiconductor wafer thereon, a rotary mechanical portion for rotating the susceptor, a gas introduction pipe for introducing a film-forming gas into the processing furnace, and a gas exhaust pipe for exhausting the film-forming gas, the apparatus for reduced-pressure epitaxial growth further comprising a purging gas introduction pipe for purging the interior of the rotary mechanical portion, a purging gas exhaust pipe for exhausting the gas introduced through the purging gas introduction pipe, a pressure adjusting valve provided in the purging gas exhaust pipe, a pressure gauge for detecting the pressure in the rotary mechanical portion, and an arithmetic/control unit for executing an arithmetic operation based upon the detected pressure and for controlling the opening degree of the pressure adjusting valve provided in the purging gas exhaust pipe, so that the pressure in the rotary mechanical portion assumes a proper value.