To provide a method for obtaining polycrystalline thin film which aligns c-axis of the crystal grain useful for the formation of oxide superconductor perpendicularly to the film forming surface of substrate, in addition, also aligns a-axis or b-axis of crystal axis of the crystal grain along the surface parallel to the film forming surface and is excellent in crystalline orientation.

This method forms the polycrystalline thin film of multiple oxide having a pyrochlore crystalline structure represented by composition formula of YZrO, GdZrO or EuZrO on the film forming surface of polycrystalline substrate. Therein, the temperature of the polycrystalline substrate is retained to a specified temperature of 90-300°C and the thin film is formed by the ion beam assist method. In this polycrystalline thin film obtained by the method, a grain boundary oblique angle constituted by the same crystalline axis of respective crystal grains along the surface parallel to the film forming surface of the polycrystalline substrate is ≤20°, Therein, EuZrO is useful, too.