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.