PURPOSE: To enable formation of a good epitaxial thin film at a phase of a high superconduction transition temperature of large (n) of Cu regarding formation of a Cu oxide superconductive thin film (Bi2Sr2Can-1CunOx).

CONSTITUTION: (1): In formation of a copper oxide superconductor with a layer structure, a process for forming unit lattice at a specified period and forming crystal of one copper layer thereon is provided when crystal of two or more copper layers is formed in unit lattice. (2): The specified period is decided by degree of attenuation of RHEED amplitude by in-site observation during formation. (3): Formation of crystal of two or more copper layers in unit lattice and formation of crystal of one copper layer are repeated alternately.