The invention provides an air conditioning device, which is provided with a heat pump refrigerating cycle comprising an outdoor unit provided with a compressor, a four-way valve, a pressure reducer and an outdoor heat exchanger, and at least one indoor unit provided with an indoor heat exchanger, which are connected by a refrigerant circuit; and the pressure reducer is arranged between the indoorheat exchanger and the outdoor heat exchanger. The air conditioning device is provided with a first bypass circuit for connecting a piping between the indoor heat exchanger and the pressure reducer and a piping between the four-way valve and the outdoor heat exchanger, wherein the first bypass circuit is provided with a two-way valve and a refrigerant heater; and a second bypass circuit for connecting a piping between the four-way valve and the indoor heat exchanger, a part of a piping between the compressor and the four-way valve, and a piping between the pressure reducer and the outdoor heatexchanger, wherein the second bypass circuit is provided with a two-way valve. When the outdoor heat exchanger defrosts, the two-way valve of the first bypass circuit is opened, so that the refrigerant heated by the refrigerant heater flows to a first bypass at the suction side of the compressor to run, and the two-way valve of the second bypass circuit is opened, so that the refrigerant runs through a second bypass of the outdoor heat exchanger.