A method of forming a metal oxide film by the plasma CVD method and which includes reacting chiefly an organometal by a glow discharge in a low output region and, then, reacting the organometal with an oxidizing gas by the glow discharge in a high-output region to form a metal oxide film on the surface of a plastic substrate via an organic layer. This method forms a thin film having excellent adhesiveness, softness and flexibility on the surface of a plastic substrate relying on the plasma CVD method.