A renewal method of an air-conditioning unit for vehicle in which an air-conditioning unit using a former refrigerant disposed in a frame mounted on a vehicle is renewed to an air-conditioning unit using an alternative refrigerant, the renewal method including a removal step of: a removing the existing air-conditioning unit from the frame; an assembly step of disposing the new air-conditioning unit, which is configured so as to be capable of fitting in the frame, in the frame; and a filling step of filling the alternative refrigerant into the new air-conditioning unit. The circulating amount of refrigerant in the new air-conditioning unit is increased so as to be larger than that in the previous air-conditioning unit, and the heat exchange capacity per unit volume of each of the indoor heat exchanger and the outdoor heat exchanger is made larger than that before the renewal.