Abstract: A radiation ray detector includes an electrode substrate includes a transparent substrate, a plurality of thin film transistors and a plurality of collecting capacitors formed on the transparent substrate, respectively, an insulation layer formed on the transparent substrate including these thin film transistors and collecting capacitors, and a plurality of photoelectric conversion elements connected to respective thin film transistors and converting visible light into an electrical signal. A scintillator layer is formed on the electrode substrate. A protective layer comprises a reflective layer formed on the scintillator layer and containing a thermoplastic polymer compound and a titanium oxide powder contained therein in an amount of 70 wt % or more, an adhesive layer formed on the surface of the electrode substrate including the reflective layer, and a moisture-proof layer adhered to the adhesive layer and having a moisture transmittance of 0.5 g/m2/day or less at 40° C. and 90% RH.