First and second engines ENG1 and ENG2; first and second transmissions TM1 and TM2 shifting the output of the first and second engines; first and second one-way clutches OWC1 and OWC2 that are provided in each output portion of the first and second transmissions; a driving target member 11 commonly connected to the output members 121 of the first and second one-way clutches via clutch mechanisms CL1 and CL2 and transmits the rotational power transmitted to the output members of the one-way clutches to the driving wheel 2; a main motor/generator MG1 connected to the member 11; a sub motor/generator MG2 connected to the output shaft S1 of the first engine; a battery 8 sending/receiving the electric power between both motor/generators; a synchronization mechanism 20 connecting/disconnecting the member 11 and the output shaft S2 of the second engine; and a controller 5.