An air-conditioning apparatus comprising: a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, an expansion device, and a refrigerant-side passage of a heat exchanger related to heat medium are connected in series and through which a heat-source-side refrigerant circulates; a heat medium circulating circuit in which a heat-medium-side passage of the heat exchanger related to heat medium, a pump, a use-side heat exchanger, and a heat medium flow control device are connected and through which a heat medium circulates; detecting means including a pressure detecting device (40a, 40b) provided on the suction side of the pump; a controller configured to perform integrated control of the operation of the air-conditioning apparatus on the basis of information detected by the detecting means and transmitted to the controller, wherein the compressor and the heat-source-side heat exchanger are arranged in an outdoor unit, wherein the heat exchanger related to heat medium, the expansion device, the pump, and the heat medium flow control device are arranged in a heat medium relay unit, wherein the use-side heat exchanger is arranged in an indoor unit, and wherein the heat medium circulating circuit is a closed circuit, characterized in that the maximum pump head Pp of the pump is 175 kPa or more, and the controller is configured such that a pressure near at least a suction side of the pump and a pressure near at least a highest position in the heat medium circulating circuit can be set to a charged pressure that is maintained equal to or higher than an atmospheric pressure during operation of the pump; such that a detected pressure detected by the pressure detecting device (40a, 40b) is always maintained equal to or higher than a specific pressure that is higher than 0 [kPa G]; and such that, when the detected pressure detected by the pressure detecting device (40a, 40b) is equal to the specific pressure or when it is estimated that the detected pressure detected by the pressure detecting device (40a, 40b) is equal to or lower than the specific pressure, a rotation speed of the pump is reduced or an opening area of the heat medium flow control device is increased. a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, an expansion device, and a refrigerant-side passage of a heat exchanger related to heat medium are connected in series and through which a heat-source-side refrigerant circulates; a heat medium circulating circuit in which a heat-medium-side passage of the heat exchanger related to heat medium, a pump, a use-side heat exchanger, and a heat medium flow control device are connected and through which a heat medium circulates; detecting means including a pressure detecting device (40a, 40b) provided on the suction side of the pump; a controller configured to perform integrated control of the operation of the air-conditioning apparatus on the basis of information detected by the detecting means and transmitted to the controller, wherein the compressor and the heat-source-side heat exchanger are arranged in an outdoor unit, wherein the heat exchanger related to heat medium, the expansion device, the pump, and the heat medium flow control device are arranged in a heat medium relay unit, wherein the use-side heat exchanger is arranged in an indoor unit, and wherein the heat medium circulating circuit is a closed circuit, characterized in that the maximum pump head Pp of the pump is 175 kPa or more, and the controller is configured such that a pressure near at least a suction side of the pump and a pressure near at least a highest position in the heat medium circulating circuit can be set to a charged pressure that is maintained equal to or higher than an atmospheric pressure during operation of the pump; such that a detected pressure detected by the pressure detecting device (40a, 40b) is always maintained equal to or higher than a specific pressure that is higher than 0 [kPa G]; and such that, when the detected pressure detected by the pressure detecting device (40a, 40b) is equal to the specific pressure or when it is estimated that the detected pressure detected by the pressure detecting device (40a, 40b) is equal to or lower than the specific pressure, a rotation speed of the pump is reduced or an opening area of the heat medium flow control device is increased.