The amount of gas evacuation from a reaction chamber of an apparatus for manufacturing epitaxial wafers is controlled to any one of: a first amount of gas evacuation when an epitaxial film formation process is performed in the reaction chamber; a second amount of gas evacuation smaller than the first amount of gas evacuation when a gate valve is opened to load or unload a wafer between the reaction chamber and a wafer transfer chamber; and a third amount of gas evacuation larger than the first amount of gas evacuation until a purge process for a gas in the reaction chamber is completed after the epitaxial film formation process is completed in the reaction chamber.