A heat exchanger for an air conditioning device includes flat tubes, a vertically extending header collecting tube connected to the flat tubes, and fins joined to the flat tubes. The header collection tube has a loop structure including partition members, inflow ports, and upper and lower communicating passages. The partition members partition first and second spaces. The flat tubes are connected at the first spaces. The inflow ports are located in lower parts of the first spaces. The upper communicating passages communicate the upper parts of the first and second spaces to guide refrigerant from the first spaces into the second spaces. The lower communicating passages communicate the lower parts of the first and second spaces to guide refrigerant from the second spaces towards spaces above the inflow ports in the first spaces to return the refrigerant from the second spaces to the first spaces.