1. A line of sight detecting device, comprising: a face direction estimation means for estimating a face direction of an object person based on a shot face image of the object person; an eye detection means for detecting a part of an eye outline in the face image of the object person; a pupil detection means for detecting a pupil in the face image of the object person; and a line of sight direction estimation means for estimating the direction of a line of sight of the object person based on the correlation of the pupil position in the eye outline and the face direction with respect to the direction of the line of sight, and the pupil position and the face direction of the object person.