Heat exchanger exchanging heat between coolant and refrigerant of different kinds in one device and providing an effective heat exchange ratio between the coolant and the refrigerant. The heat exchanger includes a refrigerant flow path having a refrigerant inlet and a refrigerant outlet, and a coolant flow path through which coolant flows to exchange heat with the refrigerant. The coolant flow path includes a first coolant flow path where first coolant flows, and a second coolant flow path where second coolant with a different kind flows. The heat exchanger is partitioned into a first heat exchange section, in which the first coolant exchanges heat with the refrigerant and a second heat exchange section, in which the second coolant exchanges heat with the refrigerant, so that the heat exchange in the first heat exchange section and the heat exchange in the second heat exchange are carried out independently.