In a method of preparing an oxide superconducting wire comprising the steps of filling up raw material powder for an oxide superconductor in a metal sheath, performing first rolling in this state for working the metal sheath into a tape, performing first heat treatment, then performing second rolling and further performing second heat treatment, diameters of rolls employed for the second rolling are made larger by at least 5 cm than those of rolls employed for the first rolling, in order to improve the critical current density of the as-formed oxide superconducting wire over its longitudinal direction.
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