Using an oxide superconductor that does not require cryogenic temperatures, a superconducting tunnel junction device is provided which can accurately control the magnitudes of critical current and step voltage necessary for electronics applications and which has good characteristics as designed. The intrinsic Josephson superconducting tunnel junction device includes an oxide superconductor defined by a general expression (I): Bi.sub.2-z Pb.sub.z Sr.sub.2 Ca.sub.n(1-x) R.sub.nx Cu.sub.n+1 O.sub.2n+6 (n.gtoreq.1, 0