A heat-pump hot-water supply apparatus comprising: a refrigerant circuit in which refrigerant compressed by a compressor (1A, 1B) and decompressed by expansion valves (5A, 5B) circulates through a closed circuit including an air heat exchanger and a water heat exchanger and in which a state of the refrigerant is repeatedly changed between liquid and gas by switching a circulating direction of the refrigerant by using four-way valves (2A, 2B); a water circuit in which water pumped out by a pump absorbs heat from the refrigerant at the water heat exchanger to become hot water and then the hot water is supplied to a load; and a controller configured to control a rotation speed of the compressor (1A, 1B) and opening degrees of the expansion valves (5A, 5B), wherein the air heat exchanger comprises a first heat exchanger and a second heat exchanger, the first heat exchanger being configured to allow a larger amount of air to pass through the first heat exchanger than an amount of air to pass through the second heat exchanger, and the expansion valves (5A, 5B) comprise a first expansion valve and a second expansion valve, the first expansion valve being connected to the first heat exchanger, the second expansion valve being connected to the second heat exchanger, characterized in that the controller is configured to perform control to supply and stop supplying the refrigerant to the first heat exchanger and the second heat exchanger by opening and closing the first expansion valve and the second expansion valve to thereby regulate a position on which frost deposits and an amount of the frost at the air heat exchanger, and the controller is configured to control the opening degrees of the first expansion valve and the second expansion valve to stop supplying the refrigerant to either one of the first heat exchanger and the second heat exchanger when the outdoor air temperature is in a first temperature range in which frosting is likely to occur, and supply the refrigerant to both of the first heat exchanger and the second heat exchanger when the outdoor air temperature is in a second temperature range being different from the first temperature range. a refrigerant circuit in which refrigerant compressed by a compressor (1A, 1B) and decompressed by expansion valves (5A, 5B) circulates through a closed circuit including an air heat exchanger and a water heat exchanger and in which a state of the refrigerant is repeatedly changed between liquid and gas by switching a circulating direction of the refrigerant by using four-way valves (2A, 2B); a water circuit in which water pumped out by a pump absorbs heat from the refrigerant at the water heat exchanger to become hot water and then the hot water is supplied to a load; and a controller configured to control a rotation speed of the compressor (1A, 1B) and opening degrees of the expansion valves (5A, 5B), wherein the air heat exchanger comprises a first heat exchanger and a second heat exchanger, the first heat exchanger being configured to allow a larger amount of air to pass through the first heat exchanger than an amount of air to pass through the second heat exchanger, and the expansion valves (5A, 5B) comprise a first expansion valve and a second expansion valve, the first expansion valve being connected to the first heat exchanger, the second expansion valve being connected to the second heat exchanger, characterized in that the controller is configured to perform control to supply and stop supplying the refrigerant to the first heat exchanger and the second heat exchanger by opening and closing the first expansion valve and the second expansion valve to thereby regulate a position on which frost deposits and an amount of the frost at the air heat exchanger, and the controller is configured to control the opening degrees of the first expansion valve and the second expansion valve to stop supplying the refrigerant to either one of the first heat exchanger and the second heat exchanger when the outdoor air temperature is in a first temperature range in which frosting is likely to occur, and supply the refrigerant to both of the first heat exchanger and the second heat exchanger when the outdoor air temperature is in a second temperature range being different from the first temperature range. stop supplying the refrigerant to either one of the first heat exchanger and the second heat exchanger when the outdoor air temperature is in a first temperature range in which frosting is likely to occur, and supply the refrigerant to both of the first heat exchanger and the second heat exchanger when the outdoor air temperature is in a second temperature range being different from the first temperature range.