The oxide superconductor according to an embodiment of the present invention is provided with an oxide superconducting layer that includes: a single crystal which has a continuous perovskite structurethat includes barium, copper, and at least one rare earth element selected from the group consisting of yttrium, lanthanum, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, which includes praseodymium in a portion of the site of the rare earth element in the perovskite structure, and which has a molar ratio of the praseodymium to the sum of the at least one rare earth element and praseodymium of 0.00000001 to 0.2; 2.0*1015 atoms/cc to 5.0*1019 atoms/cc of fluorine ; and 1.0*1017 atoms/cc to 5.0*1020 atoms/cc of carbon.