An indoor unit of an air conditioner, comprising: a housing comprising: a chassis; and a face frame connected to the chassis, a lower portion of the face frame defining an opening; an air passage member disposed on the chassis and exposed from the opening; and a lower panel comprising: an air outlet communicated with the air passage member, wherein a side of the lower panel on a front-rear direction is rotatably connected to a side edge of the opening or a side of the air passage member, and another side of the lower panel is detachably connected to another side edge of the opening or another side of the air passage member, and the lower panel is rotated to open or cover the opening for exposing or shielding the air passage member; characterised by: a heat exchanger installed in the housing; a refrigerant pipe connected with the heat exchanger and comprising a connector; and a cover plate, characterized in that the chassis comprises a dismounting hole, in that the lower panel comprises an avoiding hole corresponding to the dismounting hole, and the connector of the refrigerant pipe is exposed from the dismounting hole and the avoiding hole, and in that the cover plate is detachably connected to a lower periphery of the avoiding hole for closing or opening the avoiding hole and the dismounting hole. a housing comprising: a chassis; and a face frame connected to the chassis, a lower portion of the face frame defining an opening; a chassis; and a face frame connected to the chassis, a lower portion of the face frame defining an opening; an air passage member disposed on the chassis and exposed from the opening; and a lower panel comprising: an air outlet communicated with the air passage member, wherein a side of the lower panel on a front-rear direction is rotatably connected to a side edge of the opening or a side of the air passage member, and another side of the lower panel is detachably connected to another side edge of the opening or another side of the air passage member, and the lower panel is rotated to open or cover the opening for exposing or shielding the air passage member; characterised by: a heat exchanger installed in the housing; a refrigerant pipe connected with the heat exchanger and comprising a connector; and a cover plate, characterized in that the chassis comprises a dismounting hole, in that the lower panel comprises an avoiding hole corresponding to the dismounting hole, and the connector of the refrigerant pipe is exposed from the dismounting hole and the avoiding hole, and in that the cover plate is detachably connected to a lower periphery of the avoiding hole for closing or opening the avoiding hole and the dismounting hole. a heat exchanger installed in the housing; a refrigerant pipe connected with the heat exchanger and comprising a connector; and a cover plate, characterized in that the chassis comprises a dismounting hole, in that the lower panel comprises an avoiding hole corresponding to the dismounting hole, and the connector of the refrigerant pipe is exposed from the dismounting hole and the avoiding hole, and in that the cover plate is detachably connected to a lower periphery of the avoiding hole for closing or opening the avoiding hole and the dismounting hole.