An air-conditioning apparatus comprising: a refrigerant circuit in which a compressor for compressing heat source-side refrigerant, a refrigerant channel switching device for switching a circulation path of the heat source-side refrigerant, a heat source side heat exchanger for performing heat exchange of the heat source-side refrigerant, an expansion device for adjusting a pressure of the heat source-side refrigerant, and one or more intermediate heat exchangers for performing heat exchange between the heat source-side refrigerant and a heat medium different from the heat source-side refrigerant are connected by pipes; a heat medium circuit in which one or more pumps for circulating the heat medium to be used for the heat exchange performed by the one or more intermediate heat exchangers, a plurality of use-side heat exchangers for performing heat exchange between the heat medium and air in an air-conditioned space, a plurality of heat medium flow rate control devices for adjusting a flow rate of the heat medium, and a plurality of channel switching devices (22, 23) for switching passages of the heat medium heated or cooled to the use-side heat exchangers are connected by pipes, the heat medium circuit including one or more air purge valves (40, 43) configured to release air from inside the heat medium circuit; and a controller (52, 57); characterized in that the controller is configured to perform an air purge operation in which the refrigerant circuit heats the heat medium, and the one or more pumps of the heat medium circuit are driven thereby removing air from the heat medium circuit, wherein the controller (52, 57) is configured to perform an air purge operation in a selected channel by controlling the opening degrees of the plurality of heat medium flow rate control devices with the plurality of heat medium flow rate control devices to be either increased to the maximum opening degree or to be closed for the non-selected channels, wherein the selected channel is a channel formed by pipes that connect a channel switching device of the plurality of channel switching devices, a heat medium flow rate control device of the plurality of heat medium flow rate control devices the opening degree of which is increased to a maximum, and a use-side heat exchanger of the plurality of use-side heat exchangers. a refrigerant circuit in which a compressor for compressing heat source-side refrigerant, a refrigerant channel switching device for switching a circulation path of the heat source-side refrigerant, a heat source side heat exchanger for performing heat exchange of the heat source-side refrigerant, an expansion device for adjusting a pressure of the heat source-side refrigerant, and one or more intermediate heat exchangers for performing heat exchange between the heat source-side refrigerant and a heat medium different from the heat source-side refrigerant are connected by pipes; a heat medium circuit in which one or more pumps for circulating the heat medium to be used for the heat exchange performed by the one or more intermediate heat exchangers, a plurality of use-side heat exchangers for performing heat exchange between the heat medium and air in an air-conditioned space, a plurality of heat medium flow rate control devices for adjusting a flow rate of the heat medium, and a plurality of channel switching devices (22, 23) for switching passages of the heat medium heated or cooled to the use-side heat exchangers are connected by pipes, the heat medium circuit including one or more air purge valves (40, 43) configured to release air from inside the heat medium circuit; and a controller (52, 57); characterized in that the controller is configured to perform an air purge operation in which the refrigerant circuit heats the heat medium, and the one or more pumps of the heat medium circuit are driven thereby removing air from the heat medium circuit, wherein the controller (52, 57) is configured to perform an air purge operation in a selected channel by controlling the opening degrees of the plurality of heat medium flow rate control devices with the plurality of heat medium flow rate control devices to be either increased to the maximum opening degree or to be closed for the non-selected channels, wherein the selected channel is a channel formed by pipes that connect a channel switching device of the plurality of channel switching devices, a heat medium flow rate control device of the plurality of heat medium flow rate control devices the opening degree of which is increased to a maximum, and a use-side heat exchanger of the plurality of use-side heat exchangers.