A hybrid drive system configured with a power split device that performs a differential operation with at least three rotating elements including an input rotating element, a reaction force rotating element, and an output rotating element that is connected to the output member so that driving force is transmitted. A reduction gear that performs a differential operation with at least four rotating elements including an input rotating element, a stationary element, a first output rotating element, and a second output rotating element. A control portion selects an operating mode of the hybrid drive system, from among a first split mode, and a second split mode.