In a photoelectric conversion device, in order to suppress alteration of its properties during a long time use, lower the decrease of the S/N ratio due to a dark current output, and shorten image-pickup cycles, MIS type photoelectric conversion elements using an amorphous semiconductor material are connected with an electric power source for applying bias for photoelectric conversion, an electric power for resetting an accumulated electric charge, and a setting point for applying zero bias at the time of non-operation of the element through a switch. Emitted x-rays from an x-ray source, which is a first light source, come into collision against phosphor after being transmitted through an object body to be inspected and then are absorbed in the phosphor to be converted into visible light rays. The visible light rays from the phosphor are radiated to the photoelectric conversion elements. Prior to reading out of the x-ray image, an LED light source is lighted. Switches are used for turning on the x-ray source and the LED light source. In this embodiment, there is a reading-out period and a non-reading-out period; the x-ray source is turned on during the reading-out period, and the LED light source is turned on during the non-reading-out period.