A radiation image detector includes: a photoconductive layer that generates electric charges when irradiated by recording electromagnetic waves which have passed through an electrode layer; and detecting electrodes, for detecting signals corresponding to the electric charges generated in the photoconductive layer. The radiation image detector further includes: dielectrics that cover the edges of the detecting electrodes, the edges being the side surfaces and portions of surfaces continuous with the side surfaces of the detecting electrodes, that face the photoconductive layer; and a charge injection preventing layer, which is a conductor with respect to electric charges of the same polarity as the electric charges accumulated during recording of the image information, and an insulator with respect to electric charges of the opposite polarity from the accumulated electric charges, provided to cover at least the surfaces of the detecting electrodes that face the photoconductive layer which are not covered by the dielectric.