PURPOSE: To discriminate a pattern at high speed by executing the processing of position detection and feature extraction asynchronously with a V synchronizing signal, and executing the partial read-out of a picture in the feature extraction, and in addition, providing two systems of picture memory units.

CONSTITUTION: Two systems of the picture memories 6, 8, and a switching means 4 to switch these, and two systems of position detection circuit 9, 10 are provided, and in the picture feature quantity extraction, only a binary picture in a prescribed area from which a feature is desired to extract by a window pattern memory 11 is read out from the picture memories 6, 8 without synchronizing with the V synchronizing signal, and the feature is extracted. Thus, while the detection of position correction quantity, the extraction of the feature quantity, and the decision by the feature quantity are executed in respect of picture data read out from the picture memory of one side, the picture data can be fetched into the picture memory of the other side, and the pattern can be discriminated at high speed.