Disclosed herein is a method of preparing an oxide superconducting wire comprising the steps of coating a powder material for forming an oxide superconductor with a metal, performing deformation processing on the metal-coated powder material thereby obtaining a tape-type wire material, superposing a plurality of such tape-type wire materials, performing first heat treatment on the plurality of superposed tape-type wire materials while simultaneously diffusion-bonding the metallic coats to each other, then performing deformation processing on the plurality of superposed tape-type wire materials, and performing second heat treatment on the plurality of deformation-processed tape-type wire materials. Preferably the oxide superconductor to be obtained is a bismuth oxide superconductor having a 2223 composition in a composition of Bi-Sr-Ca-Cu or (Bi,Pb)-Sr-Ca-Cu, and the powder material consists of a superconducting phase, which is mainly composed of a 2212 phase, and non-superconducting phases.