1. A person's portrait generation device comprising: an image input section which picks up a two-dimensional image containing a person's face by using an image sensor; a head area extracting section which extracts a head area from a differential image of a plurality of the two-dimensional images picked up by the image input section; a feature detection section which detects position of characteristic features of the face within the extracted head area; a face outline determining section which determines a border between a face outline and a background within the head area; an image processing section which generates a person's portrait in which the characteristics in the person's face is emphasized based upon the two-dimensional image by using data acquired in the head area extracting section, the feature detection section and the face outline determining section.