To provide a low-cost and secure key code management system of a vehicle which eliminates the risk of leakage of the key code through the Internet.

A vehicle-mounted control unit 200 compares an authentication card ID recorded in the authentication card 212 with an authentication card ID stored in an ID storage memory 204 by communicating with the authentication card 212. When the authentication is OK, the key code is created in the ID storage memory 204. The vehicle-mounted control unit 200 communicates with an ID communications part 104 in a mobile telephone 100, stores the key code stored in the ID storage memory 204 in an ID storage memory 107 through the ID storage memory control part 106 of the mobile telephone 100, and then determines whether the registration is proper or improper. If it is proper, the registration is completed.