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.