A method for manufacturing an oxide superconductor thin film is disclosed, which comprises the steps of: (1) preparing a substrate; depositing an oxide superconductor thin film on said substrate by directing a beam containing constituent elements of an oxide superconductor to said substrate; and supplying excited oxygen to or near a thin film deposition site on said substrate during the deposition of said thin film, wherein said beam is selected from the group consisting of an ion beam, neutral particle beam, molecular beam, cluster beam and cluster ion beam, and wherein said excited oxygen is produced by means of generating discharge in an oxygen gas or oxygen-containing gas or by irradiating an oxygen gas or oxygen-containing gas with a beam.