An air-conditioning apparatus comprising: - a primary-side refrigerant circuit in which a compressor, first flow switching means, a heat source-side heat exchanger, an expansion mechanism, and an intermediate heat exchanger are connected by refrigerant pipes, and through which a primary-side refrigerant flows; and - a secondary-side refrigerant circuit in which a pump, a use-side heat exchanger, second flow switching means (10a to lOd), and the intermediate heat exchanger are connected by refrigerant pipes, and through which a secondary-side refrigerant different from the primary-side refrigerant flows, - wherein the intermediate heat exchanger has a plurality of heat transfer units (7a, 7b) and third flow switching means (11a to 11c, 12a to 12c), - wherein the heat transfer units (7a, 7b) are adapted to perform heat exchange so that the primary-side refrigerant absorbs heat from the secondary-side refrigerant in a cooling operation, and that the primary-side refrigerant radiates heat to the secondary-side refrigerant in a heating operation, - wherein the first flow switching means are adapted to switch a refrigerant flow path so that the primary-side refrigerant discharged from the compressor flows to the heat source-side heat exchanger in the cooling operation, and switch a refrigerant flow path so that the primary-side refrigerant discharged from the compressor flows to the intermediate heat exchanger in the heating operation, characterized in that the second flow switching means (11a to 11c, 12a to 12c) are adapted to switch a flow direction of the secondary-side refrigerant flowing into the intermediate heat exchanger, and wherein the third flow switching means (11a to 11c, 12a to 12c) are adapted to switch a refrigerant flow path in the cooling operation so that the primary-side refrigerant and the secondary-side refrigerant flow through the heat transfer units (7a, 7b) in parallel; and wherein the third flow switching means (11a to 11c, 12a to 12c) are adapted to switch a refrigerant flow path in the heating operation so that the primary-side refrigerant and the secondary-side refrigerant flow through the heat transfer units (7a, 7b) in series, such that a cross-sectional area of a refrigerant flow path through which the primary-side refrigerant flows becomes larger in the cooling operation than that of in the heating operation. - a primary-side refrigerant circuit in which a compressor, first flow switching means, a heat source-side heat exchanger, an expansion mechanism, and an intermediate heat exchanger are connected by refrigerant pipes, and through which a primary-side refrigerant flows; and - a secondary-side refrigerant circuit in which a pump, a use-side heat exchanger, second flow switching means (10a to lOd), and the intermediate heat exchanger are connected by refrigerant pipes, and through which a secondary-side refrigerant different from the primary-side refrigerant flows, - wherein the intermediate heat exchanger has a plurality of heat transfer units (7a, 7b) and third flow switching means (11a to 11c, 12a to 12c), - wherein the heat transfer units (7a, 7b) are adapted to perform heat exchange so that the primary-side refrigerant absorbs heat from the secondary-side refrigerant in a cooling operation, and that the primary-side refrigerant radiates heat to the secondary-side refrigerant in a heating operation, - wherein the first flow switching means are adapted to switch a refrigerant flow path so that the primary-side refrigerant discharged from the compressor flows to the heat source-side heat exchanger in the cooling operation, and switch a refrigerant flow path so that the primary-side refrigerant discharged from the compressor flows to the intermediate heat exchanger in the heating operation, characterized in that the second flow switching means (11a to 11c, 12a to 12c) are adapted to switch a flow direction of the secondary-side refrigerant flowing into the intermediate heat exchanger, and wherein the third flow switching means (11a to 11c, 12a to 12c) are adapted to switch a refrigerant flow path in the cooling operation so that the primary-side refrigerant and the secondary-side refrigerant flow through the heat transfer units (7a, 7b) in parallel; and wherein the third flow switching means (11a to 11c, 12a to 12c) are adapted to switch a refrigerant flow path in the heating operation so that the primary-side refrigerant and the secondary-side refrigerant flow through the heat transfer units (7a, 7b) in series, such that a cross-sectional area of a refrigerant flow path through which the primary-side refrigerant flows becomes larger in the cooling operation than that of in the heating operation.