An air-conditioning apparatus comprising: a refrigerant circuit configured to circulate a heat source-side refrigerant, the refrigerant circuit being a refrigerant-side flow path formed by connecting, with refrigerant pipes, a compressor, a refrigerant flow switching device, a heat source-side heat exchanger, a plurality of expansion devices (16a,16b), and a plurality of intermediate heat exchangers (15a,15b) that exchange heat between the heat source-side refrigerant and a heat medium different from the refrigerant; a heat medium circuit configured to circulate the heat medium, the heat medium circuit being a heat medium-side flow path formed by connecting, with heat medium pipes, a pump (21a, 21b), a plurality of heat medium flow switching devices (22a-22d, 23a-23d), a plurality of use-side heat exchangers (26a-26d) that act as indoor units (2a-2d), a plurality of heat medium flow control devices (25a-25d), and the intermediate heat exchangers (15a, 15b); temperature detecting means (31a,31b, 34a-34d) for detecting a temperature of the heat medium sent from each of the intermediate heat exchangers (15a, 15b) to each of the use-side heat exchangers (26a-26d), and a temperature of the heat medium that has exited each of the use-side heat exchangers (26a-26d); opening degree control means for regulating a flow rate of the heat medium through each of the heat medium flow control devices (25a-25d); and characterized by further comprising computing means configured to compute a usage capacity of each of the indoor units (2a-2d) from a rotation speed of the pump (21a, 21b), an opening degree of each of the heat medium flow control devices (25a-25d), a temperature detected by the temperature detecting means (31a,31b, 34a-34d), and a power consumption of each of the indoor units (2a-2d) itself, and on a basis of the computed usage capacity and a power consumption for a common portion that is common to each of the indoor units (2a-2d), proportionally dividing the power consumption for the common portion among each of the indoor units (2a-2d), wherein the opening degree of each of the heat medium flow control devices (25a-25d) is corrected on a basis of a reference opening degree, the reference opening degree being set on a basis of a capacity of each of the indoor units (2a-2d), a suction air temperature of each of the indoor units (2a-2d), and a temperature of the heat medium sent from each of the intermediate heat exchangers (15a, 15b) to each of the use-side heat exchangers (26a-26d), or pressure sensors are attached at opposite ends of a pipe that connects each of the indoor units (2a-2d) and the heat medium relay unit, and the opening degree of each of the heat medium flow control devices (25a-25d) is corrected by determining a correction value from a difference between values detected by the sensors. a refrigerant circuit configured to circulate a heat source-side refrigerant, the refrigerant circuit being a refrigerant-side flow path formed by connecting, with refrigerant pipes, a compressor, a refrigerant flow switching device, a heat source-side heat exchanger, a plurality of expansion devices (16a,16b), and a plurality of intermediate heat exchangers (15a,15b) that exchange heat between the heat source-side refrigerant and a heat medium different from the refrigerant; a heat medium circuit configured to circulate the heat medium, the heat medium circuit being a heat medium-side flow path formed by connecting, with heat medium pipes, a pump (21a, 21b), a plurality of heat medium flow switching devices (22a-22d, 23a-23d), a plurality of use-side heat exchangers (26a-26d) that act as indoor units (2a-2d), a plurality of heat medium flow control devices (25a-25d), and the intermediate heat exchangers (15a, 15b); temperature detecting means (31a,31b, 34a-34d) for detecting a temperature of the heat medium sent from each of the intermediate heat exchangers (15a, 15b) to each of the use-side heat exchangers (26a-26d), and a temperature of the heat medium that has exited each of the use-side heat exchangers (26a-26d); opening degree control means for regulating a flow rate of the heat medium through each of the heat medium flow control devices (25a-25d); and characterized by further comprising computing means configured to compute a usage capacity of each of the indoor units (2a-2d) from a rotation speed of the pump (21a, 21b), an opening degree of each of the heat medium flow control devices (25a-25d), a temperature detected by the temperature detecting means (31a,31b, 34a-34d), and a power consumption of each of the indoor units (2a-2d) itself, and on a basis of the computed usage capacity and a power consumption for a common portion that is common to each of the indoor units (2a-2d), proportionally dividing the power consumption for the common portion among each of the indoor units (2a-2d), wherein the opening degree of each of the heat medium flow control devices (25a-25d) is corrected on a basis of a reference opening degree, the reference opening degree being set on a basis of a capacity of each of the indoor units (2a-2d), a suction air temperature of each of the indoor units (2a-2d), and a temperature of the heat medium sent from each of the intermediate heat exchangers (15a, 15b) to each of the use-side heat exchangers (26a-26d), or pressure sensors are attached at opposite ends of a pipe that connects each of the indoor units (2a-2d) and the heat medium relay unit, and the opening degree of each of the heat medium flow control devices (25a-25d) is corrected by determining a correction value from a difference between values detected by the sensors.