A neutron radiation detector for detecting neutron radiation is provided with a scintillator (13) that produces light when irradiated with radiation, an optical fiber (14) for transmitting the light produced by the scintillator (13), and a dose calculation unit (21) for calculating a neutron dose on the basis of the light transmitted by the optical fiber (14). On a wall part of the scintillator (13)-side end of the optical fiber (14), there is a reflection part (14d) for diffusely reflecting light.