1. A digital image processing apparatus comprising: a face recognition unit recognizing a first face in an image; a face index assignment unit assigning a face index to the first face if the first face is not a previously recognized face; and a relation index update unit that, if the image includes a second face, updates a relation index corresponding to the number of times the first face and second face appear together in a plurality of images, the relation index update unit comprising: a relation index assignment unit assigning the relation index to the first face if the first face does not have a relation index corresponding to the number of times the first face and the second face appear together in the plurality of images; and a relation index modifier modifying the relation index if the first face has a relation index corresponding to the number of times the first face and the second face appear together in the plurality of images.