A plurality of pieces of information related to the iris pattern of an eye can be checked against each other in a short time. Characteristic curves (S(1)-S(8)), which are in accordance with eight ring areas (A1-A8) formed by dividing an image of an iris, are generated. The polarities of the gradients of these characteristic curves are then arranged, thereby generating codes (1-8) to be checked. Each of these codes (1-8) to be checked consists of a ternary combination of +, − and zero, whereby the amount of data to be handled during the checking process can be reduced. As a result, checking the codes to be checked can be performed in a short time.
