An air-conditioning apparatus includes a refrigerant circuit formed by connecting a compressor that discharges a zeotropic refrigerant, an outdoor-side heat exchanger that exchanges heat between outside air and the refrigerant, a first expansion device that regulates the pressure of the refrigerant, and a load-side heat exchanger that exchanges heat between the air in an air-conditioning target space and the refrigerant. The air-conditioning apparatus includes a controller that has a composition computing function unit and a composition determining function unit The composition determining function unit is configured to adopt a predetermined value set in advance and related to composition as a circulating composition if the computation result is determined as incorrect, and adopt the computation result as the circulating composition if the computation result is determined as correct.