1. An image processing device comprising: subject region detection means for detecting a region, where a subject is present, as a subject region from an input image; cutting means for cutting an image of the subject region from the input image; priority calculation means for calculating a priority of each of predetermined regions on a boundary with respect to the subject region, for the input image; retrieval means for retrieving a region similar to an image of a predetermined region with a top priority from among the priorities of the predetermined regions on the boundary with respect to the subject region, from the input image after the image of the subject region is cut; recovery means for recovering the subject region by copying an image of an adjacent region that is adjacent to the region similar to the predetermined region retrieved by the retrieval means and includes a region corresponding to a region cut as the subject region, and by pasting the image obtained by copying the adjacent region onto the region that is adjacent to the predetermined region with the top priority and cut as the subject region; and composition means for combining the image of the subject region cut by the cutting means with the image with the subject region recovered by the recovery means.