The present invention provides inspection of a transmission with higher precision and in a shorter period of time. Before a finished A/T is inspected, a V/B ASSY and an ECU are inspected together by a V/B tester in a subsidiary line. A solenoid current command value (a characteristic value inherent in the A/T) for a linear solenoid of the V/B ASSY is corrected and written into the ECU through CAN communication. Spring load of a return spring SP and stroke of the piston of a hydraulic servo for a frictional engagement element are measured. Actually measured values or corrected values of the spring load and the stroke are stored. In the final inspection of the A/T a finished-product tester reads the stored characteristic values and transmits them to the ECU integrated with the A/T through CAN communication. The characteristic values are then written into the ECU. The finished-product tester inspects the finished A/T product, using the characteristic values thus written into the ECU.