An indoor unit of an air conditioner, comprising: a chassis extending along an up-down direction; a face frame comprising: an upper support ; a lower frame detachably connected to a lower end of the chassis ; two side connectors opposite to each other and located between the upper support and the lower frame ; and a panel ; a heat exchanger ; and an air outlet frame , the face frame further comprising fastening members arranged on a rear end of the upper support and detachably fastened to the upper end of the chassis , wherein an upper end of the chassis is provided with a plurality of fastening structures spaced along a left-right direction; wherein a limiting protrusion is provided on a portion of a top surface of the chassis corresponding to the fastening structure, and wherein the fastening member is provided with a limiting hole configured to receive the limiting protrusion , characterized in that the fastening structure comprises a fastening hole provided on a front wall surface of the upper end of the chassis , wherein the fastening member comprises: an elastic arm protruding downwards from a bottom surface of the rear end of the upper support and extending backwards, the elastic arm comprising: a connecting section connected with the upper support and provided with the limiting hole ; a supporting section extending downwards from a front end of the connecting section ; and an inserting section extending backwards from a lower end of the supporting section , and inserted into the fastening hole when the face frame is in an assembled state, wherein the connecting section , the supporting section and the inserting section are connected with each other in sequence. a chassis extending along an up-down direction; a face frame comprising: an upper support ; a lower frame detachably connected to a lower end of the chassis ; two side connectors opposite to each other and located between the upper support and the lower frame ; and an upper support ; a lower frame detachably connected to a lower end of the chassis ; two side connectors opposite to each other and located between the upper support and the lower frame ; and a panel ; a heat exchanger ; and an air outlet frame , the face frame further comprising fastening members arranged on a rear end of the upper support and detachably fastened to the upper end of the chassis , wherein an upper end of the chassis is provided with a plurality of fastening structures spaced along a left-right direction; wherein a limiting protrusion is provided on a portion of a top surface of the chassis corresponding to the fastening structure, and wherein the fastening member is provided with a limiting hole configured to receive the limiting protrusion , characterized in that the fastening structure comprises a fastening hole provided on a front wall surface of the upper end of the chassis , wherein the fastening member comprises: an elastic arm protruding downwards from a bottom surface of the rear end of the upper support and extending backwards, the elastic arm comprising: a connecting section connected with the upper support and provided with the limiting hole ; a supporting section extending downwards from a front end of the connecting section ; and a connecting section connected with the upper support and provided with the limiting hole ; a supporting section extending downwards from a front end of the connecting section ; and an inserting section extending backwards from a lower end of the supporting section , and inserted into the fastening hole when the face frame is in an assembled state, wherein the connecting section , the supporting section and the inserting section are connected with each other in sequence. <EOS>