To record necessary information for failure diagnosis in accordance with its priority.

Electronic-controlled subsystems 1 are connected via a communication line 3 to generate and transmit event information using each self-diagnosis function when abnormality is occurred. An arithmetic unit 8 detects abnormality in the electronic-controlled subsystems and generates the event information. After an event occurrence detection unit 10 detects event information from the arithmetic unit 8 or the event information from the other electronic-powered subsystems through a communication unit 1, a event decision unit 14 compares priority of event information covering all electronic-controlled subsystems, and commands a record data switching unit 11 to record control data regarding the event information with high priority on a data recording unit 13.