According to one embodiment, a radiation detector comprises an array substrate having thereon a photoelectric conversion element for converting fluorescence into an electrical signal and having the outermost layer covered with a protective film, a scintillator layer provided on the protective film and converting incident radiation into fluorescence, and a reflective layer filmed by coating and drying paste-like material containing light-scattering particles and a binder provided on the scintillator layer, wherein the protective film is made of a thermoplastic resin having a softening point not higher than the film formation temperature of the scintillator layer and extending on the array substrate over an area of the reflective layer.