1. An image collating apparatus, comprising: partial image feature value calculating means for calculating, on each of a plurality of partial area images set in an image, a value reflecting a pattern of the image of the partial area, and outputting the value as a partial image feature value; maximum matching score position searching means for searching, for each of a plurality of partial area images set in one of two images, for a maximum matching score position of the other of the two images, which is a position of a partial area image having the maximum matching score with the partial area image; similarity score calculating means for calculating a similarity score between the two images and outputting an image similarity score, using information related to that partial area of which positional relation amount is within a prescribed range, said positional relation amount representing positional relation between a reference position, for each of said partial areas, for measuring a position of the partial area within said one image, and said maximum matching score position corresponding to the partial area searched out by said maximum matching score position searching means; and determining means for determining whether said two images match or not, based on said image similarity score applied thereto; wherein scope of said the other image searched by said maximum matching score position searching means is selected and determined from among a plurality of partial areas set in said the other image in accordance with said partial image feature value of the partial area image set in said one image.