An indoor unit of an air conditioner comprising: a housing having a circular shape; a heat exchanger provided in the housing and configured to receive a refrigerant; a suction port provided along a central axis of the housing, and configured to guide air into the housing ; a suction panel having a circular shape, including a suction grill provided with a plurality of holes, and configured to cover the suction port ; a discharge flow passage provided in an annular region between the outside of the heat exchanger and the inner surface of the housing and in which discharged air flows; a discharge port configured to discharge air through an annular region between the housing and the suction panel ; a fan configured to draw air through the plurality of holes in the suction panel into the suction port , move the air from the suction port to the heat exchanger , move the air from the heat exchanger to the discharge port , and discharge the air from the discharge port ; a drain tray configured to collect water condensed on the heat exchanger ; a blocking region provided at one side of the discharge flow passage and arranged to extend by a pre-set length to partition the discharge port from a complete annular shape so that a part of the discharge port is blocked; a refrigerant pipe connecting unit disposed radially outside of the heat exchanger and on the blocking region , and configured to connect the heat exchanger to an external refrigerant pipe; and a drain extraction unit disposed radially outside of the heat exchanger and on the blocking region , and configured to drain the collected water from the drain tray to the outside of the indoor unit of the air conditioner. a housing having a circular shape; a heat exchanger provided in the housing and configured to receive a refrigerant; a suction port provided along a central axis of the housing, and configured to guide air into the housing ; a suction panel having a circular shape, including a suction grill provided with a plurality of holes, and configured to cover the suction port ; a discharge flow passage provided in an annular region between the outside of the heat exchanger and the inner surface of the housing and in which discharged air flows; a discharge port configured to discharge air through an annular region between the housing and the suction panel ; a fan configured to draw air through the plurality of holes in the suction panel into the suction port , move the air from the suction port to the heat exchanger , move the air from the heat exchanger to the discharge port , and discharge the air from the discharge port ; a drain tray configured to collect water condensed on the heat exchanger ; a blocking region provided at one side of the discharge flow passage and arranged to extend by a pre-set length to partition the discharge port from a complete annular shape so that a part of the discharge port is blocked; a refrigerant pipe connecting unit disposed radially outside of the heat exchanger and on the blocking region , and configured to connect the heat exchanger to an external refrigerant pipe; and a drain extraction unit disposed radially outside of the heat exchanger and on the blocking region , and configured to drain the collected water from the drain tray to the outside of the indoor unit of the air conditioner. <EOS>