The level of a respiration signal obtained from a laser sensor or the like is indicated on a respiration monitor according to an output condition set by synchronizing signal output control device. While the level of the respiration signal is indicated on the respiration monitor, a synchronizing signal output device outputs a synchronizing signal according to the output condition and the respiration signal to an X-ray control device, which controls a high-voltage generating device to energize an X-ray source to apply X-rays to an examinee.