To surely obtain the position of a perforation hole even when there are damage and stain of the perforation hole by mutually offsetting scan value and the value of a reference pattern and generating a correction signal from an absolute offset of the scan value and the reference pattern which detect optimum equality.

An evaluating device mutually offsets scan value and the value of a reference pattern, also calculates the equality degree of the scan value and the reference patter in each calculation step and generates a correction signal from an absolute offset of the scan value and the reference value which detect optimum equality. Here, it is advantageous to mutually and separately calculate horizontal and vertical deviations in order to calculate the equality degree of the scan value and the reference pattern. Therefore, a dimension line 40 is provided perpendicularly to edges that are checked respectively, and for instance, the scan value 42 of an upper edge 43 is calculated from a perforation hole 41.