Abstract: A hybrid vehicle has an internal-combustion engine; an electric motor; a generator from which rotational speed is controlled; an output shaft connected for driving drive wheels; a differential gear unit composed of at least three elements in which a first element is connected to the engine, a second element is connected to the generator, and a third element is connected to the output shaft and the electric motor; electric storage means for supplying electric power to the electric motor and for storing electric power generated in the electric motor and the generator, the electric storage means being electrically connected to both the electric motor and the generator; required minimal load judgment means for judging the required minimal load for driving the vehicle; and generator control means for controlling a rotational speed of the generator and a change rate of the rotational speed, in which the generator control means controls in response to the required minimal load judged by the required minimal load jud