1. A method of reconstructing a three-dimensional (3D) image from two-dimensional (2D) images, the method comprising: backprojecting using a pixel value corresponding to a median, from among pixel values of images where a 3D reconstruction object is two-dimensionally projected for each pixel, and generating a 3D reconstruction image; reprojecting the 3D reconstruction image and generating a 2D reprojection image; and constructing residual images, generated due to a difference between the 2D reprojection image and each of the images where the 3D reconstruction object is two-dimensionally projected, based on a predetermined search direction weight, wherein the residual images are used to reconstruct the three-dimensional (3D) image; and wherein the method is performed using at least one processor.