In response to the driver's release of an accelerator, the procedure of the invention sequentially compares an observed charge-discharge electric power Wb of a battery with two reference values Wr1 and Wr2, which are set on the basis of an input restriction Win of the battery. The procedure changes over a control mode among an ordinary state varying control (processing of and after step S160) to gradually lower a revolution speed Ne of an engine with torque output, an idling state varying control (step S220) to gradually lower the revolution speed Ne of the engine while idling the engine, and a fuel supply shutoff state varying control (step S230) to shut off fuel supply to the engine.