PURPOSE: To precisely recognize the position of an object by a method wherein three points is detected by using three reference patterns and the centroid of a polygon formed by the detected points is calculated to determine a specified point.

CONSTITUTION: Pattern matching is conducted by using a reference pattern A, and thereby the position of a pattern 6a is detected. Next, pattern matching is conducted by using a reference pattern B, and thereby the position of a pattern 6b is detected. Moreover, the position of a pattern 6c is detected by using a reference pattern C. The coordinates of the centroid of a mark pattern 2a are calculated from the coordinates of these positions. The position of a packaging pattern 3 can be calculated from the positions of mark patterns 2a and 2b. Since the centroids of the mark patterns are determined and used as the reference for recognition of the position in this way, the recognition of the position can be conducted precisely even when the size of the mark pattern is varied.