A radiation detector includes a flexible substrate, and a sensor board including a layer which is provided on a first surface of the substrate and in which a plurality of pixels, which accumulate electrical charges generated in accordance with light converted from radiation, are formed, a conversion layer that is provided on the first surface side of the sensor board to convert radiation into light, a protective film that covers at least a region ranging from a region that covers the conversion layer to a region at an outer peripheral part of a second surface opposite to the first surface of the substrate, and a supporting member that supports the region of the substrate via the protective film from the second surface side of the substrate.