1. An apparatus for unfolding a depth image, the apparatus comprising: a processor to control one or more processor-executable units: an input unit to receive inputted multiple depth images with respect to a same scene, the multiple depth images being photographed based on different modulation frequencies of a fixed photographing device; a depth fold estimator to estimate a number of depth folds based on a distance between multiple three-dimensional (3D) points of multiple pixels indicating the same location of the scene in the multiple depth images; and an output unit to output the multiple depth images from which one or more depth folds have been removed based on the estimated number of depth folds.