An oxide superconductor includes: a substrate made of a metal; an insulating intermediate layer provided on the substrate; an oxide superconducting layer provided on the intermediate layer; a metal stabilizing layer provided on the oxide superconducting layer; and a plurality of dividing grooves which divide the metal stabilizing layer and the oxide superconducting layer along a longitudinal direction of the substrate, reach the inside of the intermediate layer through the oxide superconducting layer from the metal stabilizing layer, and do not reach the substrate. The metal stabilizing layer and the oxide superconducting layer are divided to form a plurality of filament conductors by the plurality of dividing grooves, and in each dividing groove of the plurality of dividing grooves, a width of a groove opening portion of the dividing groove is equal to or greater than a width of a groove bottom portion of the dividing groove.