A diagnostic X-ray apparatus of an embodiment includes determining circuitry, projection image generating circuitry, and a display. The determining circuitry determines, based on position information of a probe of a diagnostic ultrasound apparatus acquired from the diagnostic ultrasound apparatus, at least one of an angle horizontal to a scan plane of the probe and an angle vertical to the scan plane of the probe to be an X-ray irradiation direction in processing to perform puncture using a puncture needle. The projection image generating circuitry generates, based on the position information and the X-ray irradiation direction, projection image data that projects an ultrasound image of the scan plane in the X-ray irradiation direction. The display displays X-ray image data containing the puncture needle photographed in the X-ray irradiation direction and the projection image data generated by the projection image generating circuitry.
