PURPOSE: To develop the maximum function of a drive system of an automatic transmission with torque converter by providing a retarder device on the drive system.

CONSTITUTION: In a drive system in which an automatic transmission 8 is combined with at least a torque converter 6, an induction machine 31 is provided between a parking brake device 26 for a pump impeller 6a, input shaft 20, or output shaft 25 in a drive system ranging from the pump impeller 6a of the torque converter 6 to the output shaft 25 through a turbine liner 6b, input shaft 20, and automatic transmission 8 and a case side for covering the drive system. Then the induction machine 31 is operated as an electric motor in starting and accelerating to increase a torque in the drive system, and driven supplementarily to increase the output torque properties and to increase a traveling performance, fuel consumption, and exhaust gas properties. Also the induction machine 31 is operated as a generator in traveling downhill to apply brake forcibly to the drive system. Thus low engine braking effect can be compensated.