In a counter shaft type transmission equipped with a pair of transmission gear trains, the input shaft of the first gear train is connected with the engine and the second gear train is connected with the engine via a motor. The torque of the first gear train is briefly shifted onto the second gear train while a gear change in the first gear train is accomplished. By setting the gear ratio of the second gear train to a half-position of gear ratio of the first gear train, motor capacity and battery capacity can be reduced, reducing transmission cost. Further, with the motor, torque transfer becomes possible for both up-shift and down-shift and, since continuous ratios can be achieved, drivability of an automobile improves.