A low-loss oxide superconducting wire using a reversible phenomenon is disclosed. The oxide superconducting wire is formed with a metal-coated multi-filamentary superconductor having a plurality of superconducting filaments in a matrix, in which d≦2 &mgr;m  (1), and d/(2&lgr;0′)≦1  (2), where d represents the size of the superconducting filament, and &lgr;0′ represents penetration depth of Campbell's a.c. magnetic field.