The present invention provides an X-ray generator including an X-ray tube 2 radiating primary X-rays X1 to a specimen S, a housing 3 accommodating the X-ray tube 2, an X-ray radiation area controller 4 limiting the radiation area of the primary X-rays X1 from the X-ray tube 2 to the specimen S, and a device holder 5 holding the X-ray radiation area controller 4 with respect to the housing 3. The X-ray tube includes a case 6, an electron ray source 7 generating electron rays, and a target unit 8 having a base fixed to the case and receiving electron rays through a protruding free end. The device holder has a fixed-base 5a fixed to the housing, directly under the base of the target unit, and a supporting extension 5b extending from the fixed-base in the protrusion direction of the target unit and supporting the X-ray radiation area controller.