1. A feature point location determination method comprising: a first search step of searching for locations of a plurality of feature points in a predetermined first search area in an image; a location correction step of correcting the locations of the plurality of feature points based on a geometric layout relationship among the plurality of feature points searched for by said first search step; a second search step of setting a second search area based on the locations of the plurality of feature points corrected by said location correction step and searching for locations of the feature points in the second search area; and a selection step of determining reliability of the location of each of the feature points searched for by said second search step and thereby selecting one of the location corrected by said location correction step and the location searched for by said second search step, as the location of each of the feature points to be localized.