A heat-pump hot-water supplying and air conditioning apparatus comprising: a heat-pump refrigerant system configured such that refrigerant fed by a compressor can circulate in a closed-circuit refrigerant circuit having an outdoor heat exchanger and an indoor heat exchanger, undergoing repeated gas/liquid state changes, and that is capable of selecting a cooling cycle or a heating cycle by switching a circulation direction of the refrigerant that circulates in the refrigerant circuit; and a water system provided with a hot-water tank which is connected, via a flow-path switching valve, to a hot-water circulation flow path in which water fed by a pump can absorb heat from the refrigerant at the indoor heat exchanger to be turned into hot water, the hot water being circulated to be used as a hot-water heat source, characterized in that the heat-pump hot-water supplying and air conditioning apparatus is configured such that, when the heat-pump hot-water supplying and air conditioning apparatus performs a defrosting operation by setting a refrigerant circulation direction in the refrigerant system to the cooling cycle, depending on a detected water temperature of hot water flowing in the water system, one of circulating hot water circulating in the hot-water circulation flow path and stored hot water stored in the hot-water tank is selected as water to be flowed to the indoor heat exchanger during the defrosting operation, and the stored hot water is selected when the detected water temperature is at or below a predetermined water temperature, and wherein the predetermined water temperature is corrected so as to get higher as the outdoor air temperature decreases. a heat-pump refrigerant system configured such that refrigerant fed by a compressor can circulate in a closed-circuit refrigerant circuit having an outdoor heat exchanger and an indoor heat exchanger, undergoing repeated gas/liquid state changes, and that is capable of selecting a cooling cycle or a heating cycle by switching a circulation direction of the refrigerant that circulates in the refrigerant circuit; and a water system provided with a hot-water tank which is connected, via a flow-path switching valve, to a hot-water circulation flow path in which water fed by a pump can absorb heat from the refrigerant at the indoor heat exchanger to be turned into hot water, the hot water being circulated to be used as a hot-water heat source, characterized in that the heat-pump hot-water supplying and air conditioning apparatus is configured such that, when the heat-pump hot-water supplying and air conditioning apparatus performs a defrosting operation by setting a refrigerant circulation direction in the refrigerant system to the cooling cycle, depending on a detected water temperature of hot water flowing in the water system, one of circulating hot water circulating in the hot-water circulation flow path and stored hot water stored in the hot-water tank is selected as water to be flowed to the indoor heat exchanger during the defrosting operation, and the stored hot water is selected when the detected water temperature is at or below a predetermined water temperature, and wherein the predetermined water temperature is corrected so as to get higher as the outdoor air temperature decreases.