1. An X-ray imaging apparatus, comprising: an X-ray irradiation element that irradiates an X-ray to an external subject; an X-ray imaging element that operatively takes an X-ray image on the basis of the X-ray transmitted through said subject; an image synthesis element that is operative to receive and synthesize an image by connecting in turn a plurality of strip-shape X-ray images concurrently taken while letting said X-ray irradiation element and said X-ray imaging element concurrently move along a path relative to said subject; and a first display element that displays an intermediate image imaged by said X-ray imaging element and which is successively synthesized in turn by said image synthesis element.