An X-ray generating tube includes an insulating tube having a first open end and a second open end, a cathode including an electron emission source and arranged to close the first open end of the insulating tube, an anode including a target that generates an X-ray upon collision with electron from the electron emission source and arranged to close the second open end of the insulating tube, and a tubular electrical conductive member extending from the anode in an inner space of the insulating tube. The insulating tube includes a tubular rib at a position spaced apart from the first open end and spaced apart from the second open end, and the tubular rib is arranged in a radial direction when viewed from an end of the tubular electrical conductive member on a side of the cathode.