Disclosed is an electronic control apparatus for a vehicle which includes: 1) first storage means for storing vehicle identification information unique to the vehicle; 2) second storage means for storing immobilizer identification information unique to the vehicle; 3) command receiving means for receiving, from an external control apparatus, an update command that commands the electronic control apparatus to update the vehicle identification information stored in the first storage means; and 4) information handling means for handling all the information stored in the first and second storage means. Moreover, in the electronic control apparatus, upon receipt of the update command by the command receiving means, the information handling means updates the immobilizer identification information stored in the second storage means as well as the vehicle identification information stored in the first storage means.