1. A pattern model creating method in image processing for positioning by searching an object to be searched that is similar to a pre-registered image out of an image to be searched by use of a pattern model corresponding to the registered image, the method including the steps of: extracting a plurality of edge points from the registered image; creating a plurality of continuous chains by coupling adjacent edge points among the plurality of extracted edge points; eliminating a chain with a length not larger than a predetermined length among the plurality of chains; sorting remaining chains in order based on length; selecting chains sequentially either from the smallest chain among the remaining chains or from the longest chain among the remaining chains with a predetermined number of chains; and regarding aggregation of the selected chains as a contour extracted from the registered image, to construct a pattern model for positioning, wherein the method is performed using a computer or processor.