An underlayer of a phosphor layer is disposed on a sensor panel including two-dimensionally arranged photoelectric conversion devices. The surface of the underlayer is subjected to atmospheric pressure plasma treatment. The phosphor layer is formed on the surface-treated underlayer. Then, the phosphor layer is covered with a moisture-resistant protective layer, a reflection layer, and another protective layer. Thus, the phosphor layer is prevented from peeling due to adhesion failure, and is constituted of uniformly shaped crystals by vapor deposition. A resulting radiation detecting apparatus exhibits high sensitivity and high definition, producing a uniform photoelectric conversion efficiency.