A heat pump type air conditioner comprising: an exterior unit including an exterior heat exchanger, a plurality of compressors, a four-way valve, an exterior expansion device, and an injection circuit for injecting the liquid refrigerant into each of the plurality of compressors; and a plurality of interior units, each of which includes an interior heat exchanger, connected to the exterior unit. The exterior unit further comprises device for controlling flow rate of the liquid refrigerant to be injected in accordance with number of the plurality of interior units.