Abstract: A password updating system sets the available period and the updating period of the password for each individual user according to the frequency of his accesses to the computer system, and manages password updating by urging the user in advance to change his password on the basis of these periods. There is a chronometric unit; and a password hysteresis memory unit for memorizing and managing passwords and their available periods. An update processing unit checks the input password, requests reentry if the same password exists or updates it if no same password exists, invalidates the current password if the updating period of the password has expired, and also validates invalidated passwords. There is a comparator unit for comparing the available periods of passwords and notifying the update processing unit of a request to update the password.