1. A head detecting apparatus comprising: a foreground extracting section for extracting a foreground region, in which a person has been taken, from an input image; a first main axis computing section for computing a main axis of the foreground region; a head region computing section for computing a head region included in the foreground region as a part thereof, based on the main axis of the foreground region and a shape of the foreground region; and an ellipse determining section for determining an ellipse to be applied to the head of the person, based on a shape of the head region.