1. A pattern matching method, comprising the steps of: (a) sequentially extracting patterns from an image to produce extracted patterns each having an area with an extraction pattern size, comprising the substeps of: (ai) picking a master sample image for forming a master pattern; and (aii) sequentially extracting the extracted patterns with the extraction pattern size beginning with an initial pattern in the master sample image; (b) mutually comparing each of the extracted patterns with all other patterns in the image, comprising the substeps of: (bi) comparing each of the extracted patterns wtih all other patterns in the master sample image; (bii) calculating pattern matching degrees between each of the extracted patterns and all the other patterns in the master sample image; (biii) determining a similar matching degree of each of the extracted patterns, the similar matching degree being a maximum of the pattern matching degrees between each of the extracted patterns and all the other patterns; (biv) calculating a waveform of the pattern matching degrees; (bv) differentiating the waveform of the pattern matching degrees to form a second order differential waveform; and (bvi) measuring an interval length between peaks of the second order differential waveform; (c) registering one of the extracted patterns having the similar matching degree which is a minimum, as a master pattern, when the interval length is within a predetermined range; and (d) identifying an object pattern by a pattern matching procedure between the image including the object pattern and the master pattern.