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 . <EOS>