A hybrid system includes: an engine; a motor/generator; an automatic clutch; a differential device including first, second, and third rotational elements; a first transmission mechanism; a second transmission mechanism; and a control device, the automatic clutch being provided between the engine and the first transmission mechanism, an input of the first transmission mechanism being connected to the automatic clutch and the second rotational element, the motor/generator being connected to the first rotational element, the third rotational element of the differential device being connected to the second transmission mechanism, the first and the second transmission mechanisms include the same output shaft connected to the wheels. In an electric vehicle driving mode, the control device performs control on the automatic clutch and the first and second transmission mechanisms to drive torque from the first transmission mechanism to the engine to start the engine.