1. An X-ray imaging apparatus comprising: an X-ray generation unit that generates an X-ray and irradiates a subject with the X-ray; a subject positioning rotation table unit that adjusts an angle of the subject with respect to an optical path direction of the X-ray and an incident position of the X-ray to the subject; an X-ray image detection unit that detects an X-ray transmitted through the subject; a detector positioning table unit that two-dimensionally moves and positions the X-ray image detection unit on a surface perpendicular to an X-ray; a processing unit that calculates a sectional image of the subject from a plurality of X-ray images obtained by moving the X-ray image detection unit by the detector positioning table unit; and a control unit that controls each of the units, wherein the X-ray image detection unit obtains an X-ray image while an angle of the subject with respect to the optical path direction of the X-ray is changed by the subject positioning rotation table unit, the detector positioning table unit moves the X-ray image detection unit for each time the angle reaches half rotation, and the moved X-ray image detection unit repeatedly obtains the X-ray image.