1. A feature point location estimation device comprising: an image input unit which receives input of a facial image from an external source; a parameter gradient direction computation unit which computes, from a plurality of facial image templates constituted by the positive examples and the negative examples and the facial feature point location search parameter, a gradient direction of the facial feature point location search parameter; a search parameter update unit which updates the facial feature point location search parameter by adding the computed gradient direction; a convergence determination unit which determines whether the updated facial feature point location search parameter is convergent; and a search result output unit which, when the facial feature point location search parameter is determined as being convergent, outputs a facial feature point location computed by the facial feature point location search parameter as a search result.