An imaging-condition setting part that sets a plurality of CT-image imaging conditions, including an electric amount for driving and controlling an X-ray tube during CT imaging, based on a scout image that has been imaged by irradiating X-rays from the X-ray tube, to a subject on a top board, that has been stopped at least one of said first position and said second position; and a calculating part that judges whether there are any detection elements that are expected to detect an X-ray dosage exceeding a predetermined value and outputs the judgment result when the X-ray tube is stopped at least one of the first position and the second position relative to the subject on the top board and X-rays are irradiated from the X-ray tube through driving and controlling based on the electric amount.