PURPOSE: To optionally update rationality checking logic for each credit card issuing source by an international exchange through a man/machine interface.

CONSTITUTION: An issuing source identification(ID) number registering table 1 registers and stores credit card numbers and their issuing source number in each credit card issuing source. A logical number registering part 2 registers a logical number for regulating the rationality of a credit card number in each issuing source number regulated by converting the issuing source number into a normalized number. A rationality checking table 3 executes logic judgement corresponding to the logical number and outputs a judged result. An updating processing part 4 updates the contents of the table 1 by the maintenance man's operation.