A converted reference image generated from a reference image is searched for a first corresponding point corresponding to a first standard point included in a converted standard image generated from a standard image. Based on a position of the first corresponding point in the converted reference image, a second search standard point is determined on the reference image. Further, based on phase information on each frequency component regarding a second standard area including a second standard point corresponding to the first standard point of the standard image, and based on phase information on each frequency component regarding a second reference area including the second search standard point of the reference image, the reference image is searched for a second corresponding point corresponding to the second standard point. The information on a frequency component obtained in the computation on another stage is reused in the search on the two stages above.