In a cassette-type X-ray detection device, an X-ray detector and a self diagnostic circuit are contained in a cassette casing. When the cassette-type X-ray detection device gets a shock, the self diagnostic circuit is actuated. The self diagnostic circuit reads out from the X-ray detector an offset image being a dark current image, and analyzes the offset image. The self diagnostic circuit finds out an abnormal portion from the offset image, and diagnoses whether the X-ray detector is available, unavailable, or partly available based on the size and position of the abnormal portion. Shock detection and a diagnostic result are displayed on a touch panel provided in the cassette casing, and sent to a console device via a communication unit.
