Writing method of hardware performance information of unit in vehicle

In an inspection procedure of a completed product of an automatic transmission main body (10) at a unit factory, a control system (20) transmits a control signal to an actuator (5) to receive characteristic data (hardware performance information) output in response to operation of the automatic transmission main body (10) according to the control signal. The hardware performance information of the automatic transmission main body (10) is brought into correspondence with hardware identification information, and set in a database as learning value data. The learning value data of the automatic transmission main body (10) is transferred to a vehicle factory to be aggregated in a database management system (50) at the vehicle factory. When the automatic transmission main body (10) is assembled with an electronic control device (40), learning value data of the automatic transmission main body (10) is read out based on the hardware identification information from the database management system (50), and written into an AT_ECU (44) during the inspection procedure of a completed vehicle at the vehicle factory.