An air-conditioning apparatus comprising: a refrigerant circuit in which a compressor, a refrigerant passage switching device that switches a passage of a refrigerant discharged from the compressor, a first heat exchanger, a first expansion device, and a refrigerant flow passage of a second heat exchanger are connected via a refrigerant pipe through which the refrigerant is distributed; a heat medium circuit in which a heat medium flow passage of the second heat exchanger and a heat medium sending device are connected via a heat medium pipe through which a heat medium is distributed, and to which a use side heat exchanger is connected; a heat medium passage reversing device that is disposed in the heat medium circuit and that is capable of switching a direction of the heat medium flowing through the heat medium flow passage of the second heat exchanger between a normal direction and a reverse direction; characterized in that the air-conditioning apparatus further comprises a controller that is configured to control the heat medium passage reversing device to switch the direction of the heat medium flowing through the heat medium flow passage of the second heat exchanger; and a freezing determination unit that is configured to determine whether or not there is a possibility of freezing of the heat medium flowing through the heat medium flow passage of the second heat exchanger, wherein the refrigerant suitable for flowing through the refrigerant circuit is a non-azeotropic refrigerant mixture including two or more components and having a temperature glide between a saturated gas temperature and a saturated liquid temperature at the same pressure, and wherein in a condition where the second heat exchanger serves as a cooler that cools the heat medium, the controller is configured to control the heat medium passage reversing device so that, when the freezing determination unit determines that the heat medium flowing through the heat medium flow passage of the second heat exchanger will not be frozen, the refrigerant flowing through the refrigerant flow passage of the second heat exchanger and the heat medium flowing through the heat medium flow passage of the second heat exchanger are in counter flow, and control the heat medium passage reversing device so that, when the freezing determination unit determines that there is a possibility of freezing of the heat medium flowing through the heat medium flow passage of the second heat exchanger, the refrigerant flowing through the refrigerant flow passage of the second heat exchanger and the heat medium flowing through the heat medium flow passage of the second heat exchanger are in parallel flow. a refrigerant circuit in which a compressor, a refrigerant passage switching device that switches a passage of a refrigerant discharged from the compressor, a first heat exchanger, a first expansion device, and a refrigerant flow passage of a second heat exchanger are connected via a refrigerant pipe through which the refrigerant is distributed; a heat medium circuit in which a heat medium flow passage of the second heat exchanger and a heat medium sending device are connected via a heat medium pipe through which a heat medium is distributed, and to which a use side heat exchanger is connected; a heat medium passage reversing device that is disposed in the heat medium circuit and that is capable of switching a direction of the heat medium flowing through the heat medium flow passage of the second heat exchanger between a normal direction and a reverse direction; characterized in that the air-conditioning apparatus further comprises a controller that is configured to control the heat medium passage reversing device to switch the direction of the heat medium flowing through the heat medium flow passage of the second heat exchanger; and a freezing determination unit that is configured to determine whether or not there is a possibility of freezing of the heat medium flowing through the heat medium flow passage of the second heat exchanger, wherein the refrigerant suitable for flowing through the refrigerant circuit is a non-azeotropic refrigerant mixture including two or more components and having a temperature glide between a saturated gas temperature and a saturated liquid temperature at the same pressure, and wherein in a condition where the second heat exchanger serves as a cooler that cools the heat medium,