An X-ray imaging apparatus includes an X-ray generation unit configured to irradiate an object with X-rays in a rectangular shape, and an imaging unit which has a rectangular imaging plane and is configured to receive the X-rays transmitted through the object as an X-ray image, wherein the imaging unit is arranged on a plane which is spaced a predetermined distance apart from the X-ray generation unit and perpendicular to an X-ray reference axis such that a center of an irradiation field and a center of the imaging plane match with each other and rotational angles of the irradiation field and the imaging plane around the X-ray reference axis match with each other, by matching at least three visible light beams which have directionality and are irradiated from the X-ray generation unit, with distance indexes provided in the imaging unit.