Abstract: A substrate is heated in a crystal growth vessel evacuated to a ultrahigh vacuum, and gases containing component elements of a crystal to be grown on the substrate are introduced into the vessel under predetermined conditions to cause successive epitaxial growth of single molecular layers, the number of growth cycles being automatically controlled. A mass analyzer is disposed opposite to the substrate in the vessel so that the progress of crystal growth can be incessantly traced and evaluated for each of the molecular layers. An etchant gas introduction nozzle extends into the vessel to make etching treatment of the surface of the substrate in the evacuated vessel prior to the crystal growth.