Abstract: After processing, a target feature point is detected. Information about a target feature point includes the position of the ridge containing a vicinal feature point relative to the position of the ridge containing the target feature point in addition to the position, type, and direction of the target feature point. Then, the information is checked in a matching process, and the vicinal feature point is checked on a feature point contained in a ridge matching in position the ridge of the target feature point. When the target feature point and the vicinal feature point match in position and direction, and are different in type only, the mark has a value indicating a matching level. Then, a matching result of the vicinal feature points is obtained as a matching mark, and it is determined whether the target feature point is matching by determining whether the matching mark is equal to or larger than a threshold.