The present invention relates to an X-ray image processing device and an X-ray image processing method using a small X-ray detector, and the purpose of the present invention is to provide an X-ray image processing device and method for reconfiguring, as three-dimensional images, projection images having a width smaller than the width of a field of view (FOV) of an X-ray image device, specifically, having a width of less than 50%. To this end, the device of the present invention comprises: a control unit for performing control such that an X-ray source and an X-ray detector obtain m(m is an integer of 2 or more) number of consecutive split projection images at each of preset n (n is an integer of 1 or more) number of capturing angles, while rotating around a rotary shaft and facing each other； a projection image synthesizing unit for generating a synthetic projection image by synthesizing the m number of split projection images obtained in correspondence to each capturing angle； and an image reconfiguration unit for generating a reconfiguration image by reconfiguring the synthetic projection image.
