Disclosed herein are an X-ray imaging apparatus and a control method thereof in which a clear 3D volume of an object may be acquired when the 3D volume of the object is reconstructed from X-ray images acquired by radiating X-rays to the object. The X-ray imaging apparatus includes an image processing unit configured to acquire a plurality of X-ray images of an object from converted electrical signals, group the plurality of X-ray images into groups of X-ray images acquired from the same cardiac phase, and perform image reconstruction of each of the groups acquired as a result of the grouping.