An X-ray generator includes an X-ray tube, an X-ray tube accommodation portion, and a power source unit having an internal substrate supplying a voltage to the X-ray tube sealed inside an insulating block. Insulating oil is enclosed in a space defined by an upper surface of the insulating block and an inner surface of the X-ray tube accommodation portion. A high-voltage power supply unit connected to a target support portion is disposed on the upper surface. At least one protrusion portion protruding to an insulating valve side beyond a boundary portion where the high-voltage power supply unit, the upper surface, and the insulating oil meet and surrounding the high-voltage power supply unit is provided on the upper surface. An apex portion of the protrusion portion is separated from an imaginary plane including an end portion of the insulating valve and extending in a direction orthogonal to a tube axis.