An input coordinate sequence is acquired by sampling a handwritten input pattern at predetermined intervals, and a pattern expressed by this input coordinate sequence is approximated by coupling a plurality of line segments to attain line segment conversion. Adjacent angle data .phi.[i] is generated based on the directions of the respective line segments. At this time, the segment line length along line segments of all the line segments is divided by a predetermined value at equal intervals, and the angles obtained from the directions of the line segments at respective division positions are defined as .phi.[i]. This .phi.[i] is compared with a standard pattern (adjacent angle distribution data) prepared in advance to obtain a matching level. In this way, more accurate pattern matching for a handwritten input, which is approximately invariant to affine transformation and can reduce the influence of discretization errors can be implemented.