An indoor unit of an air conditioner comprising: a housing, having an accommodating cavity, wherein the accommodating cavity comprises a mounting space, and a rear side of the mounting space defines a mounting opening on a side of the indoor unit closest to a wall when mounted on the wall an air passage member, detachably mounted in the accommodating cavity, wherein the air passage member comprises an outlet air frame, a wind wheel and a driving device arranged at an end in an axial direction of the wind wheel, and the mounting space is arranged on a side of the driving device away from the wind wheel, wherein the wind wheel and the driving device are mounted on the outlet air frame; a heat exchanger arranged above the air passage member; and a thermal insulation tube configured to accommodate a refrigerant tube, comprising a first tube section extending along a direction of the housing perpendicular to the axial direction of the wind wheel, and is mountable in the mounting space through the mounting opening, wherein one end of the first tube section is adjacent to the heat exchanger, and the other end of the first tube section is adjacent to a bottom of the accommodating cavity, wherein the indoor unit further comprises: an accommodating box, arranged in the mounting space; wherein a rear side of the accommodating box defines a first opening communicated with the mounting opening, and the first tube section is mounted in the accommodating box through the mounting opening and the first opening, wherein the accommodating box comprises: a first side plate, an inner wall surface of the first side plate being facing the mounting opening; and wherein the indoor unit further comprises: an electrical control box, characterised in that the electrical box is arranged on an outer wall surface of the first side plate. a housing, having an accommodating cavity, wherein the accommodating cavity comprises a mounting space, and a rear side of the mounting space defines a mounting opening on a side of the indoor unit closest to a wall when mounted on the wall an air passage member, detachably mounted in the accommodating cavity, wherein the air passage member comprises an outlet air frame, a wind wheel and a driving device arranged at an end in an axial direction of the wind wheel, and the mounting space is arranged on a side of the driving device away from the wind wheel, wherein the wind wheel and the driving device are mounted on the outlet air frame; a heat exchanger arranged above the air passage member; and a thermal insulation tube configured to accommodate a refrigerant tube, comprising a first tube section extending along a direction of the housing perpendicular to the axial direction of the wind wheel, and is mountable in the mounting space through the mounting opening, wherein one end of the first tube section is adjacent to the heat exchanger, and the other end of the first tube section is adjacent to a bottom of the accommodating cavity, wherein the indoor unit further comprises: an accommodating box, arranged in the mounting space; wherein a rear side of the accommodating box defines a first opening communicated with the mounting opening, and the first tube section is mounted in the accommodating box through the mounting opening and the first opening, wherein the accommodating box comprises: a first side plate, an inner wall surface of the first side plate being facing the mounting opening; and wherein the indoor unit further comprises: an electrical control box, characterised in that the electrical box is arranged on an outer wall surface of the first side plate.