An indoor unit of a wall-mounted air conditioner comprising: a chassis; a screen assembly; and a cleaning assembly disposed at one end of the screen assembly and connected with the screen assembly by a fastening structure, wherein the fastening structure is a detachable structure, that comprises a first threaded structure; wherein the cleaning assembly is mounted on the chassis, or the screen assembly is mounted on the chassis, or the cleaning assembly and the screen assembly are both mounted on the chassis; wherein the screen assembly comprises a grille assembly, and wherein the cleaning assembly comprises a cleaning box disposed below the grille assembly and comprising a third connecting member extending upwardly from an edge of an opening of the cleaning box, and wherein the first threaded structure comprises a first locking screw penetrating the third connecting member and threaded with one end of the grille assembly; wherein the chassis comprises: a bottom wall defining an accommodating space; and a rear side wall connected to a rear side of the bottom wall, wherein a lower portion of the cleaning assembly is mounted in the accommodating space; wherein an upper portion of the cleaning assembly is connected with the rear side wall by a second threaded structure, the cleaning assembly comprises a fourth connecting member protruded from the cleaning box and extended away from the other end of the screen assembly; and wherein the second threaded structure comprises a second locking screw penetrating the fourth connecting member and threaded with the rear side wall; and wherein the fourth connecting member is integrally formed on a rear side edge of the third connecting member. a chassis; a screen assembly; and a cleaning assembly disposed at one end of the screen assembly and connected with the screen assembly by a fastening structure, wherein the fastening structure is a detachable structure, that comprises a first threaded structure; wherein the cleaning assembly is mounted on the chassis, or the screen assembly is mounted on the chassis, or the cleaning assembly and the screen assembly are both mounted on the chassis; wherein the screen assembly comprises a grille assembly, and wherein the cleaning assembly comprises a cleaning box disposed below the grille assembly and comprising a third connecting member extending upwardly from an edge of an opening of the cleaning box, and wherein the first threaded structure comprises a first locking screw penetrating the third connecting member and threaded with one end of the grille assembly; wherein the chassis comprises: a bottom wall defining an accommodating space; and a rear side wall connected to a rear side of the bottom wall, a bottom wall defining an accommodating space; and a rear side wall connected to a rear side of the bottom wall, wherein a lower portion of the cleaning assembly is mounted in the accommodating space; wherein an upper portion of the cleaning assembly is connected with the rear side wall by a second threaded structure, the cleaning assembly comprises a fourth connecting member protruded from the cleaning box and extended away from the other end of the screen assembly; and wherein the second threaded structure comprises a second locking screw penetrating the fourth connecting member and threaded with the rear side wall; and wherein the fourth connecting member is integrally formed on a rear side edge of the third connecting member.