A heat exchanger includes fins arranged in parallel with each other with a predetermined spacing along the rotational axis direction of a blower. Heat exchanger tubes are inserted into the fins to form rows along a longitudinal direction of the fins connected to each other along the airflow direction, to form refrigerant channels. A branch portion is provided to connection portions of the heat exchanger tubes to increase or decrease the number of paths in the refrigerant channels. Refrigerant flows through each of the refrigerant channels passing through paths mutually different at least at one portion between the refrigerant inlet and the refrigerant outlets, flows along one direction from the windward-side row to the leeward-side row, or from the leeward-side row to the windward-side row in the airflow direction, in sequence between rows. One-path portion is provided in the most windward-side row heat exchanger tubes. The fins are in close contact with a refrigerant outlet case when the heat exchanger is operated as a condenser, and a connection piping are thermally separated by separation means.