A planar X-ray detector including an X-ray-electric charge conversion film converting an incident X-ray into an electric charge, a pixel electrode contiguous to the X-ray-electric charge conversion film and arranged for every pixel, and a switching element connected to the pixel electrode. Also included is a signal line connected to the switching element, and a scanning line supplying a driving signal to the switching element. Further, the X-ray-electric charge conversion film contains phosphor particles, a photosensitive material, and a carrier transfer material.