An X-ray tube includes a rod-shaped anode which includes a target receiving electrons and generating X-rays and has a main body portion extending in a direction of a tube axis; a vacuum housing which accommodates a distal end side of the anode having the target disposed therein and in which a proximal end side of the anode is fixed by a housing coupling portion; and a cover electrode which is disposed inside the vacuum housing, is coupled to the anode by a cover coupling portion, and surrounds the housing coupling portion. The anode has a third diameter increasing portion protruding from a front surface of the main body portion in a direction intersecting the tube axis. The cover coupling portion is disposed closer to the proximal end side of the anode than the third diameter increasing portion.