A neutron detector includes a plurality of neutron detecting element sections, each of the neutron detecting element sections having; a superconducting element including a substrate having at least one of surfaces thereof formed of a dielectric material, a strip line of the superconducting material formed on the surface and electrodes formed at opposed ends of the strip line, resistance determining sections for determining generation of heat resulting from a nuclear reaction between a superconducting element in the strip line and neutrons, through detection of change in a resistance value of said strip line, heat dissipation setting sections provided on a back side portion of the substrate opposite to the surface having the strip line formed thereon, the heat dissipation setting sections setting dissipation characteristics of the heat resulting from the nuclear reaction, and the heat dissipation characteristics being differentiated from each other between/among the neutron detecting element sections.