Abstract: A method of fabricating a superconducting wire includes forming a buffer layer on the substrate, the buffer layer including an Al2O3 layer, the Al2O3 layer being formed by reactive magnetron sputtering in which first oxygen gas as reactant gas and a sputtering target made of aluminium metal are used, the Al2O3 layer being formed while being supplied the first oxygen gas at a first concentration, the first concentration being a concentration of the first oxygen gas at which an emission intensity of Al in plasma near a surface of the sputtering target is not less than 25% and not more than 80% of a first reference value, the first reference value being the emission intensity of Al at which the concentration of the first oxygen gas is zero; and forming a superconducting layer above the buffer layer.