The present invention utilizes magnesium diboride (MgB2) or (Mg1−xMx)B2 as a superconductivity thin film which can be applied to a rapid single flux quantum (RSFQ) circuit. A method for manufacturing a superconductor incorporating therein a superconductivity thin film, begins with preparing a single crystal substrate. Thereafter, a template film is formed on top of the substrate, wherein the template has a hexagonal crystal structure. The superconductivity thin film of MgB2 or (Mg1−xMx)B2 is formed on top of the template film. If Mg amount in the superconductivity thin film is insufficient, Mg vapor is flowed on the surface of the superconductivity thin film while a post annealing process is carried out at the temperature ranging from 400° C. to 900° C.