To provide a measuring method which does not provide constraint to a search angle of turning pattern matching, also reduces the load of pattern matching processing and depends upon image recognition that is effective, also is not influenced by various fluctuation factors and performs measurement with high accuracy.

After calculating the center of gravity I of a pattern of an input image, it is arranged so that the center of gravity I coincide with the center of gravity P of a pattern image (reference image). Patterns on a straight line that goes through a turning center with the center of gravity of a pattern as the turning center and a density distribution of background are taken out and preliminarily registered. The straight line is turned around the center of gravity of the pattern of the input image, the density distribution is cut out on the straight line and it is performed pattern matching with the registered density distribution of a turned pattern. This processing is fast because of one-dimensional pattern matching. Then, it is possible to perform turning pattern matching which does not need to provide the constraint of a turning angle, also is hard to be influenced by various fluctuation factors, is stable and also has high accuracy.