PURPOSE: To read character of the same type in the same system, by constituting a shape matrix as a feature quantity on a basis of the circumscribed quadrangle of a sampled character.

CONSTITUTION: When an alphabetic character pattern P1, numeric pattern P2, and a noise N exist in an effective area UP, quadrangles Q1, Q2, and Q3 circumscribed to patterns P1 and P2 and the noise N respectively are provided. Since sizes of circumscribed quadrangles for alphabetic characters and numbers are determined preliminarily respectively, noise components of which the side of the circumscribed quadrangle is different from that of standard circumscribed quadrangles are separated easily, and characters of the same type are read in this system.