An indoor unit for an air conditioner comprising: an indoor unit body which has an opening at its bottom surface and accommodates therein a heat exchanger, a drain pan, a blower, and the like; and a dress panel which covers the opening at the bottom of the indoor unit body and is exposed to the inside of a room, wherein the dress panel comprises: a rectangular panel body having a suction opening in its center and blower openings provided on all sides of the suction opening; an opening provided in each corner of the panel body; a corner panel fitted in the opening so as to be freely removable; and characterised by furthermore comprising: a corner panel fitting/removal mechanism which fits/removes the corner panel to/from the opening of the panel body, and the corner panel fitting/removal mechanism comprises: a swing member attached to the panel body so as to freely swingable around its middle, and having a hooking pawl at one end and an operating screw hole at the other end; an operation screw screwed into the operating screw hole in the swing member, used to incline the swing member as the operation screw is rotated in a predetermined direction, and to project an end of the corner panel from the surface of the panel body by use of the hooking pawl, thereby allowing the corner panel to be removed; and an engagement hole provided in the corner panel, and engaged with the hooking pawl as the operation screw is rotated in a direction opposite to the predetermined direction, and hence the swing member is inclined in an opposite direction, thereby disposing the corner panel and panel body in the same plane such that the corner panel cannot be removed. an indoor unit body which has an opening at its bottom surface and accommodates therein a heat exchanger, a drain pan, a blower, and the like; and a dress panel which covers the opening at the bottom of the indoor unit body and is exposed to the inside of a room, wherein the dress panel comprises: a rectangular panel body having a suction opening in its center and blower openings provided on all sides of the suction opening; an opening provided in each corner of the panel body; a corner panel fitted in the opening so as to be freely removable; and characterised by furthermore comprising: a corner panel fitting/removal mechanism which fits/removes the corner panel to/from the opening of the panel body, and the corner panel fitting/removal mechanism comprises: a swing member attached to the panel body so as to freely swingable around its middle, and having a hooking pawl at one end and an operating screw hole at the other end; an operation screw screwed into the operating screw hole in the swing member, used to incline the swing member as the operation screw is rotated in a predetermined direction, and to project an end of the corner panel from the surface of the panel body by use of the hooking pawl, thereby allowing the corner panel to be removed; and an engagement hole provided in the corner panel, and engaged with the hooking pawl as the operation screw is rotated in a direction opposite to the predetermined direction, and hence the swing member is inclined in an opposite direction, thereby disposing the corner panel and panel body in the same plane such that the corner panel cannot be removed. a rectangular panel body having a suction opening in its center and blower openings provided on all sides of the suction opening; an opening provided in each corner of the panel body; a corner panel fitted in the opening so as to be freely removable; and a corner panel fitting/removal mechanism which fits/removes the corner panel to/from the opening of the panel body, and the corner panel fitting/removal mechanism comprises: a swing member attached to the panel body so as to freely swingable around its middle, and having a hooking pawl at one end and an operating screw hole at the other end; an operation screw screwed into the operating screw hole in the swing member, used to incline the swing member as the operation screw is rotated in a predetermined direction, and to project an end of the corner panel from the surface of the panel body by use of the hooking pawl, thereby allowing the corner panel to be removed; and an engagement hole provided in the corner panel, and engaged with the hooking pawl as the operation screw is rotated in a direction opposite to the predetermined direction, and hence the swing member is inclined in an opposite direction, thereby disposing the corner panel and panel body in the same plane such that the corner panel cannot be removed. a swing member attached to the panel body so as to freely swingable around its middle, and having a hooking pawl at one end and an operating screw hole at the other end; an operation screw screwed into the operating screw hole in the swing member, used to incline the swing member as the operation screw is rotated in a predetermined direction, and to project an end of the corner panel from the surface of the panel body by use of the hooking pawl, thereby allowing the corner panel to be removed; and an engagement hole provided in the corner panel, and engaged with the hooking pawl as the operation screw is rotated in a direction opposite to the predetermined direction, and hence the swing member is inclined in an opposite direction, thereby disposing the corner panel and panel body in the same plane such that the corner panel cannot be removed.