In order to provide a computer program, an image processing device, and a pattern matching method that perform pattern matching at a high level of accuracy without relying on edge deformation, contrast fluctuations, etc., in one embodiment, the disclosed pattern matching method and device perform pattern matching over an image using a template produced on the basis of the below mentioned design data. The pattern matching method and device determine the characteristic quantities of the image for an inner region and/or an outer region that are divided by a line that defines the contour of a pattern, and determine positions at which said characteristic quantities satisfy predetermined conditions to be matching positions, matching position candidates, or erroneous matching positions.