PURPOSE: To improve the accuracy of pattern recognition and the recognizing processing efficiency, by improving further a calculating formula of distorted distance between a defined pattern and an input pattern by using a plane pattern map.

CONSTITUTION: A play pattern map producing section 63 produces the plane pattern map to the input pattern by executing alternately the processing using tables, I , II for a required number of times. A distortion calculating section 66 processes the matching from the definition pattern to the input pattern and then, the inverse matching. When the coincidence between the definition pattern and the input pattern is high, in other words, between less distorted picture elements, the processing of duplicated calculation for both matchings is hardly executed, allowing to decrease the redundant elements included in the distortion. A minimum value selecting section 68 compares the distortion improved for the redundancy as stated above between the patterns, obtains a minimum value and outputs it as the result of recognition.