1. A depth value restoration method comprising: a preprocessing step of conducting image preprocessing with regard to a depth map and its corresponding color image, so as to respectively obtain a candidate object region including a foreground image from the depth map and its corresponding color image; a determination step of determining, based on an area ratio of an invalid region to the candidate object region of the depth map, whether it is necessary to conduct a region growing process with respect to the candidate object region of the depth map; a growing step of, if it is determined that it is necessary to conduct the region growing process with respect to the candidate object region of the depth map, then conducting, based on image information of the depth map and its corresponding color image, the region growing process with respect to the candidate object region of the depth map; and after the region growing process is conducted with respect to the candidate object region of the depth map, a restoration step of, regarding the grown candidate object region, conducting, based on the image information of the depth map and its corresponding color image, a depth value restoration process with respect to a candidate region.