An air conditioner includes a compressor and a heat exchanger. The heat exchanger includes a first header pipe to have a refrigerant compressed by the compressor to flow therein, a heat exchange unit including a plurality of first refrigeration tubes and a plurality of second refrigeration tubes to thermally exchange the refrigerant with air, a plurality of first header branch pipes coupling the first header pipe with corresponding first refrigeration tubes in the heat exchange unit, a bypass pipe to have the refrigerant, thermally exchanged in the heat exchange unit, passing therethrough in the air cooling operation, and a second header pipe to have the refrigerant passing through the bypass pipe to flow therein. A plurality of second header branch pipes couples the second header pipe with corresponding second refrigeration tubes in the heat exchange unit, where at least two first refrigeration tubes have at least one second refrigeration tube therebetween.