An air-conditioning apparatus comprising: at least one intermediate heat exchanger that exchanges heat between a refrigerant changing in two phases or a refrigerant in a supercritical state and a heat medium such as water and anti-freezing fluid different from said refrigerant; a refrigeration cycle in which a compressor, an outdoor heat exchanger, at least one expansion valve, and a refrigerant-side channel of said intermediate heat exchanger are connected via a pipeline through which said refrigerant flows, a heat-medium circulation circuit in which a heat-medium side channel of said intermediate heat exchanger, a pump, and a use-side heat exchanger are connected via a pipeline through which said heat medium flows, and a controller, characterized in that the controller is configured to control said refrigeration cycle and said heat-medium circuit so that an air-conditioning load of said use-side heat exchanger becomes a predetermined value, and in said heat-medium circulation circuit, a heat-medium temperature detection portion to detect a temperature of said heat-medium flowing through said heat-medium circulation circuit is provided on an outlet side of a heat medium channel of the use-side heat exchanger, wherein the controller is configured to detect leakage of the heat medium from said heat-medium circulation circuit by comparing the temperature of said heat-medium detected by said heat-medium temperature detection portion with a first value and second value of a threshold temperature (T1, T2), wherein the controller is configured to determine, during a heating operation, if the temperature of said heat-medium detected by said heat-medium temperature detection portion falls under a value of a first threshold temperature, that the heat medium is leaking from said heat-medium circulation circuit for heating; and if the temperature of said heat-medium detected by said heat-medium temperature detection portion is larger than the value of the first threshold temperature, that the heat medium is not leaking from said heat-medium circulation circuit for heating; and during a cooling operation, if the temperature of said heat-medium detected by said heat-medium temperature detection portion is larger than a value of a second threshold temperature, that the heat medium is leaking from said heat-medium circulation circuit for cooling; and if the temperature of said heat-medium detected by said heat-medium temperature detection portion is not larger than the value of the second threshold temperature, that the heat medium is not leaking from said heat-medium circulation circuit for cooling. at least one intermediate heat exchanger that exchanges heat between a refrigerant changing in two phases or a refrigerant in a supercritical state and a heat medium such as water and anti-freezing fluid different from said refrigerant; a refrigeration cycle in which a compressor, an outdoor heat exchanger, at least one expansion valve, and a refrigerant-side channel of said intermediate heat exchanger are connected via a pipeline through which said refrigerant flows, a heat-medium circulation circuit in which a heat-medium side channel of said intermediate heat exchanger, a pump, and a use-side heat exchanger are connected via a pipeline through which said heat medium flows, and a controller, characterized in that the controller is configured to control said refrigeration cycle and said heat-medium circuit so that an air-conditioning load of said use-side heat exchanger becomes a predetermined value, and in said heat-medium circulation circuit, a heat-medium temperature detection portion to detect a temperature of said heat-medium flowing through said heat-medium circulation circuit is provided on an outlet side of a heat medium channel of the use-side heat exchanger, wherein the controller is configured to detect leakage of the heat medium from said heat-medium circulation circuit by comparing the temperature of said heat-medium detected by said heat-medium temperature detection portion with a first value and second value of a threshold temperature (T1, T2), wherein the controller is configured to determine, during a heating operation, if the temperature of said heat-medium detected by said heat-medium temperature detection portion falls under a value of a first threshold temperature, that the heat medium is leaking from said heat-medium circulation circuit for heating; and if the temperature of said heat-medium detected by said heat-medium temperature detection portion is larger than the value of the first threshold temperature, that the heat medium is not leaking from said heat-medium circulation circuit for heating; and during a cooling operation, if the temperature of said heat-medium detected by said heat-medium temperature detection portion is larger than a value of a second threshold temperature, that the heat medium is leaking from said heat-medium circulation circuit for cooling; and if the temperature of said heat-medium detected by said heat-medium temperature detection portion is not larger than the value of the second threshold temperature, that the heat medium is not leaking from said heat-medium circulation circuit for cooling.