(1) Orthogonal transformation is applied to sample images based on the images of a normalized orthogonal system, and component groups are determined. A plurality of comparison target images are selected from an input image, and a partial normalized orthogonal system is created from the normalized orthogonal system by decreasing the dimensions. (2) Based on the partial normalized orthogonal system, orthogonal transformation is applied to the comparison target images, so as to determine the partial component group for each comparison target image. A comparison target image having high consistency with one of the sample images is extracted by comparison and collation between these partial component groups and the partial component groups which include each element of each partial normalized orthogonal system among component groups of each sample image. And a new comparison target image group is selected near the extracted image, and a new partial normalized orthogonal system is created by increasing the dimensions. Then (2) is repeated.