A vehicle power output device for driving a first and second rotary electric machine in an efficient range in a wide driving region and for eliminating the need for a complicated mechanism and control. A planetary gear mechanism combines the rotational drive force of a first shaft rotationally driven by a first rotary electric machine and the rotational drive force of a second shaft rotationally driven by a second rotary electric machine and transmits the combined rotational drive force to a drive shaft with the rotational speed increased. The rotational drive force of the second shaft in the forward direction is transmitted to the planetary gear mechanism via a first one-way clutch unit and a first power transmitting mechanism. The rotational drive force of the second shaft in the opposite direction is transmitted to the drive shaft via a second one-way clutch unit and a second power transmitting mechanism.