According to one embodiment, a radiation detector includes a substrate, a scintillator layer, a moisture-proof body and an adhesive layer. The substrate is partitioned into at least an active area and a bonding area. The substrate includes a photoelectric conversion element located in the active area and configured to convert fluorescence to an electrical signal, an organic resin protective layer located at an outermost layer in the active area, and an inorganic protective film located at an outermost layer of the bonding area. The scintillator layer is formed on the organic resin protective layer so as to cover the photoelectric conversion element and configured to convert radiation to the fluorescence. The moisture-proof body is formed so as to cover the scintillator layer. The adhesive layer is formed on the inorganic protective film and bonds the moisture-proof body to the substrate.