In a vehicle of the invention, the lower between a first permissive water temperature based on an outside air temperature Tout and an elapsed time since system activation and a second permissive water temperature based on a target air outlet temperature in an air conditioning system is set to an intermittent operation permissive water temperature. When a cooling water temperature of an engine is not lower than the set intermittent operation permissive water temperature, intermittent operation of the engine is permitted. When the cooling water temperature of the engine is lower than the set intermittent operation permissive water temperature, on the other hand, intermittent operation of the engine is prohibited. This arrangement ensures appropriate control of the intermittent operation of the engine and thus effectively improves the fuel efficiency of the vehicle.