To improve fuel consumption at actuation of an air conditioner.

At deceleration of a vehicle, energy Er the air conditioner requires at traveling so as to maintain predetermined air conditioning state A1 and A2 and energy Es the air conditioner requires at stoppage of the vehicle are calculated by following expression; Er=(compressor drive energy+fan drive energy at traveling)/power generation efficiency ηr, and Es=(compressor drive energy+fan derive energy at stopping)/power generation efficiency ηs. When the energy Er is smaller than the energy Es, regenerated energy is supplied to a compressor 7 with priority so that a number of revolutions of the compressor 7 rises to a predetermined number of revolutions. Thereby, an evaporator 11 frosts and compressor drive power at stoppage of the vehicle can be reduced.