To provide a superconducting X-ray detector capable of carrying out a measurement by a high energy resolution by restraining a reduction in a sensitivity by a self magnetic field. A superconducting X-ray detector comprising a temperature detector 6 for detecting a temperature change by heat generated when an X-ray is absorbed, and a heat link 3 for controlling a heat flow amount of escaping the generated heat to a support board i, wherein the temperature detector 6 comprises a heat conducting multilayer thin film, the superconducting X-ray detector is constituted by a structure of providing a superconductor layer 4 above the heat link 3 and providing an insulating member 2 between the superconductor layer 4 and the temperature detector 6, the superconductor layer 4 and the temperature detector 6 are connected by a superconducting wiring 7 and uses materials by which superconducting transition temperatures of the superconductor layer 4 and the superconducting wiring 7 are higher than a superconducting transition temperature of the temperature detector 6.