An air-conditioning apparatus, comprising: a compressor; a heat source side heat exchanger; a plurality of expansion devices; a plurality of heat exchangers related to heat medium; a pump; and one or more use side heat exchangers, wherein a refrigerant circuit circulating a heat source side refrigerant is formed by connecting the compressor, the heat source side heat exchanger, the expansion devices, and refrigerant side passages of the heat exchangers related to heat medium with a refrigerant piping, a heat medium circuit circulating a heat medium is formed by connecting the pump, the one or more use side heat exchangers, and heat medium side passages of the heat exchangers related to heat medium with a heat medium piping, and the heat source side refrigerant and the heat medium exchange heat in the heat exchangers related to heat medium, the air-conditioning apparatus, further comprising: a use side heat medium flow control device and a first heat medium flow switching device, disposed on each outlet side of heat medium passages of the one or more use side heat exchangers; characterized by a heat medium backflow prevention device disposed on each inlet side of the heat medium passages of the one or more use side heat exchangers, wherein a flow direction of the heat medium flowing in the heat medium piping is the same irrespective of operation mode, and wherein the heat medium backflow prevention device is constituted by a check valve that prevents the heat medium from backflowing against the flow direction of the heat medium. a compressor; a heat source side heat exchanger; a plurality of expansion devices; a plurality of heat exchangers related to heat medium; a pump; and one or more use side heat exchangers, wherein a refrigerant circuit circulating a heat source side refrigerant is formed by connecting the compressor, the heat source side heat exchanger, the expansion devices, and refrigerant side passages of the heat exchangers related to heat medium with a refrigerant piping, a heat medium circuit circulating a heat medium is formed by connecting the pump, the one or more use side heat exchangers, and heat medium side passages of the heat exchangers related to heat medium with a heat medium piping, and the heat source side refrigerant and the heat medium exchange heat in the heat exchangers related to heat medium, the air-conditioning apparatus, further comprising: a use side heat medium flow control device and a first heat medium flow switching device, disposed on each outlet side of heat medium passages of the one or more use side heat exchangers; characterized by a heat medium backflow prevention device disposed on each inlet side of the heat medium passages of the one or more use side heat exchangers, wherein a flow direction of the heat medium flowing in the heat medium piping is the same irrespective of operation mode, and wherein the heat medium backflow prevention device is constituted by a check valve that prevents the heat medium from backflowing against the flow direction of the heat medium. a use side heat medium flow control device and a first heat medium flow switching device, disposed on each outlet side of heat medium passages of the one or more use side heat exchangers; characterized by a heat medium backflow prevention device disposed on each inlet side of the heat medium passages of the one or more use side heat exchangers, wherein a flow direction of the heat medium flowing in the heat medium piping is the same irrespective of operation mode, and wherein the heat medium backflow prevention device is constituted by a check valve that prevents the heat medium from backflowing against the flow direction of the heat medium.