An air-conditioning apparatus comprising: refrigerating cycle systems each connecting a compressor for compressing a refrigerant, a refrigerant flow path switching device for switching the circulation path of the refrigerant, a heat source side heat exchanger for exchanging heat for the refrigerant, an expansion device for adjusting the pressure of the refrigerant, and heat exchangers related to heat medium which exchange heat between the refrigerant and heat medium different from the refrigerant to be able to make the heat medium different in temperature respectively, by piping so as to constitute a refrigerant circuit; and heat medium side systems each connecting heat medium sending devices for circulating the heat medium for the heat exchangers related to heat medium, use side heat exchangers for exchanging heat between the heat medium and air of an air-conditioning target space and flow path switching units for switching the heat medium which passes through heat exchangers related to heat medium to the use side heat exchangers, by piping so as to constitute a heat medium circulation circuit, wherein the refrigerating cycle systems and the heat medium side systems are constituted by combining outdoor units each having the compressor, the refrigerant flow path switching device and the heat source side heat exchanger; heat medium relay units each having the heat exchangers related to heat medium and the heat medium sending devices; indoor units each having the corresponding use side heat exchanger; characterized in that the flow path switching units have heat medium flow path switching devices (22, 23); wherein the air-conditioning apparatus comprises a heat exchange means controller which is configured such that cooling capacity and heating capacity are respectively added up to total values, the cooling capacity and the heating capacity each being necessary to the heat medium for a load related to each heat exchange of the use side heat exchangers, and on the base of the total values, cooling capacity and heating capacity are assigned to each refrigerating cycle system, the cooling capacity and the heating capacity being supplied to the heat medium, and wherein the number of compressors needed for supplying the cooling capacity and the heating capacity is determined on the base of the total values when the compressors operate with the maximum operation efficiency, and the determined number of the refrigerating cycle systems operates. refrigerating cycle systems each connecting a compressor for compressing a refrigerant, a refrigerant flow path switching device for switching the circulation path of the refrigerant, a heat source side heat exchanger for exchanging heat for the refrigerant, an expansion device for adjusting the pressure of the refrigerant, and heat exchangers related to heat medium which exchange heat between the refrigerant and heat medium different from the refrigerant to be able to make the heat medium different in temperature respectively, by piping so as to constitute a refrigerant circuit; and heat medium side systems each connecting heat medium sending devices for circulating the heat medium for the heat exchangers related to heat medium, use side heat exchangers for exchanging heat between the heat medium and air of an air-conditioning target space and flow path switching units for switching the heat medium which passes through heat exchangers related to heat medium to the use side heat exchangers, by piping so as to constitute a heat medium circulation circuit, wherein the refrigerating cycle systems and the heat medium side systems are constituted by combining outdoor units each having the compressor, the refrigerant flow path switching device and the heat source side heat exchanger; heat medium relay units each having the heat exchangers related to heat medium and the heat medium sending devices; indoor units each having the corresponding use side heat exchanger; characterized in that the flow path switching units have heat medium flow path switching devices (22, 23); wherein the air-conditioning apparatus comprises a heat exchange means controller which is configured such that cooling capacity and heating capacity are respectively added up to total values, the cooling capacity and the heating capacity each being necessary to the heat medium for a load related to each heat exchange of the use side heat exchangers, and on the base of the total values, cooling capacity and heating capacity are assigned to each refrigerating cycle system, the cooling capacity and the heating capacity being supplied to the heat medium, and wherein the number of compressors needed for supplying the cooling capacity and the heating capacity is determined on the base of the total values when the compressors operate with the maximum operation efficiency, and the determined number of the refrigerating cycle systems operates.