1. An apparatus for obtaining a high dynamic range (HDR) image, the apparatus comprising: an image sensor which generates a first image by applying different exposure times for units of a predetermined region; an image separating unit which separates the first image into images, each of which is composed of regions having an identical exposure time; an image restoring unit which restores the separated images in such a way that each of the separated images has a resolution that is the same as a resolution of the first image; and an image synthesizing unit which synthesizes the restored images into a second image.