A radiation image detector includes a first electrode for transmitting an electromagnetic wave for recording, the electromagnetic wave carrying a radiation image, a photoconductive layer for recording, a plurality of charge-collecting electrodes, and a substrate. The photoconductive layer for recording generates charges by irradiation with the electromagnetic wave for recording that has been transmitted through the first electrode, and has amorphous selenium as its major component and further contains alkali metal. The first electrode, the photoconductive layer for recording, the plurality of charge-collecting electrodes and the substrate are superposed one on another in this order. Further, an amorphous selenium layer is provided as an anti-crystallization layer between the first electrode and the photoconductive layer for recording. The amorphous selenium layer contains at least one element selected from the group consisting of As, Sb and Bi at 5% to 40%.