An air conditioner comprising: a main body defining an outer appearance; an indoor heat exchanger disposed within the main body and comprising: a plurality of heat exchangers (200a, 200b, 200c) being vertically spaced apart from each other, wherein a first heat exchanger of the plurality of heat exchangers (200a, 200b, 200c)) is disposed at the lowest position and is configured to have slower speed of air flowing therethrough than the speed of air flowing through each of one or more other heat exchangers (200b, 200c); a plurality of branch tubes (210a, 210b, 210c), comprising a first branch tube and at least one or more other branch tubes (210b, 210c), respectively connected to the plurality of heat exchangers (200a, 200b, 200c) and configured for guiding a refrigerant into the heat exchangers (200a, 200b, 200c) in a cooling mode: a circulation tube connected to the plurality of branch tubes (210a, 210b, 210c) and configured to guide the refrigerant; a bypass tube connecting the first branch tube of the plurality of branch tubes (210a, 210b, 210c), which is connected to the first heat exchanger disposed at the lowest position, to the circulation tube, the bypass tube being configured to bypass refrigerant, which is introduced from the first heat exchanger into the first branch tube, into the circulation tube in a heating mode; a branch tube valve disposed in said first branch tube to adjust an amount of the refrigerant flowing into said first branch tube; and a bypass valve disposed at the bypass tube for adjusting an amount of the refrigerant flowing into the bypass tube, wherein said first branch tube has a smaller diameter than each of the one or more other branch tubes (210b, 210c), wherein the air conditioner is configured to direct a portion of the refrigerant, in a cooling mode, from the circulation tube into the first heat exchanger through said first branch tube; and, in a heating mode, from the first heat exchanger disposed at the lowest position into the circulation tube through the bypass tube. a main body defining an outer appearance; an indoor heat exchanger disposed within the main body and comprising: a plurality of heat exchangers (200a, 200b, 200c) being vertically spaced apart from each other, wherein a first heat exchanger of the plurality of heat exchangers (200a, 200b, 200c)) is disposed at the lowest position and is configured to have slower speed of air flowing therethrough than the speed of air flowing through each of one or more other heat exchangers (200b, 200c); a plurality of heat exchangers (200a, 200b, 200c) being vertically spaced apart from each other, wherein a first heat exchanger of the plurality of heat exchangers (200a, 200b, 200c)) is disposed at the lowest position and is configured to have slower speed of air flowing therethrough than the speed of air flowing through each of one or more other heat exchangers (200b, 200c); a plurality of branch tubes (210a, 210b, 210c), comprising a first branch tube and at least one or more other branch tubes (210b, 210c), respectively connected to the plurality of heat exchangers (200a, 200b, 200c) and configured for guiding a refrigerant into the heat exchangers (200a, 200b, 200c) in a cooling mode: a circulation tube connected to the plurality of branch tubes (210a, 210b, 210c) and configured to guide the refrigerant; a bypass tube connecting the first branch tube of the plurality of branch tubes (210a, 210b, 210c), which is connected to the first heat exchanger disposed at the lowest position, to the circulation tube, the bypass tube being configured to bypass refrigerant, which is introduced from the first heat exchanger into the first branch tube, into the circulation tube in a heating mode; a branch tube valve disposed in said first branch tube to adjust an amount of the refrigerant flowing into said first branch tube; and a bypass valve disposed at the bypass tube for adjusting an amount of the refrigerant flowing into the bypass tube, wherein said first branch tube has a smaller diameter than each of the one or more other branch tubes (210b, 210c), wherein the air conditioner is configured to direct a portion of the refrigerant, in a cooling mode, from the circulation tube into the first heat exchanger through said first branch tube; and, in a heating mode, from the first heat exchanger disposed at the lowest position into the circulation tube through the bypass tube. a circulation tube connected to the plurality of branch tubes (210a, 210b, 210c) and configured to guide the refrigerant; a bypass tube connecting the first branch tube of the plurality of branch tubes (210a, 210b, 210c), which is connected to the first heat exchanger disposed at the lowest position, to the circulation tube, the bypass tube being configured to bypass refrigerant, which is introduced from the first heat exchanger into the first branch tube, into the circulation tube in a heating mode; a branch tube valve disposed in said first branch tube to adjust an amount of the refrigerant flowing into said first branch tube; and a bypass valve disposed at the bypass tube for adjusting an amount of the refrigerant flowing into the bypass tube, wherein said first branch tube has a smaller diameter than each of the one or more other branch tubes (210b, 210c), wherein the air conditioner is configured to direct a portion of the refrigerant, in a cooling mode, from the circulation tube into the first heat exchanger through said first branch tube; and, in a heating mode, from the first heat exchanger disposed at the lowest position into the circulation tube through the bypass tube.