An indoor unit comprising: a casing having a front surface and holder accommodation portions opening on the front surface and recessed so as to slope upward approaching toward a back side of the casing; arm holders which are inserted into the holder accommodation portions from a front side of the casing and which are installed inside of the holder accommodation portions so as to be detachable therefrom; arms which are inserted into the holder accommodation portions from the front side of the casing and each of which a first end is held by the arm holder so that the arm is allowed to turn around an axis extending in a longitudinal direction of the casing; and an inlet panel to which a second end of each of the arms is fixed, wherein the range of movement of the arms around the axis is set between a closed position where the inlet panel is disposed in a manner of overlapping the front surface of the casing and openings of the holder accommodation portions are closed by the inlet panel, and an open position where the inlet panel is disposed forward and upward from the front surface of the casing and the front surface of the casing is exposed, characterized in that the indoor unit further includes bolts each fastened to the casing from the front side thereof to fix the arm holder to the casing, wherein the holder accommodation portions each include: a holder support portion having a support surface supporting the arm holder from below thereof; and a first engagement portion which is flexible and extending upward from the support surface in a direction intersecting the support surface, and wherein the arm holders each include: a holding portion which is placed on the support surface and holding the arm so as to allow to be turned around the axis; a second engagement portion which is integrally formed on the holding portion so as to be protruded therefrom and which is engaged with the first engagement portion in a condition where the holding portion is inserted into the holder accommodation portion; and a fixed portion which is integrally formed on the holding portion so as to be protruded therefrom and which is installed on the holder support portion by fastening the bolt to the casing. a casing having a front surface and holder accommodation portions opening on the front surface and recessed so as to slope upward approaching toward a back side of the casing; arm holders which are inserted into the holder accommodation portions from a front side of the casing and which are installed inside of the holder accommodation portions so as to be detachable therefrom; arms which are inserted into the holder accommodation portions from the front side of the casing and each of which a first end is held by the arm holder so that the arm is allowed to turn around an axis extending in a longitudinal direction of the casing; and an inlet panel to which a second end of each of the arms is fixed, wherein the range of movement of the arms around the axis is set between a closed position where the inlet panel is disposed in a manner of overlapping the front surface of the casing and openings of the holder accommodation portions are closed by the inlet panel, and an open position where the inlet panel is disposed forward and upward from the front surface of the casing and the front surface of the casing is exposed, characterized in that the indoor unit further includes bolts each fastened to the casing from the front side thereof to fix the arm holder to the casing, wherein the holder accommodation portions each include: a holder support portion having a support surface supporting the arm holder from below thereof; and a first engagement portion which is flexible and extending upward from the support surface in a direction intersecting the support surface, and a holder support portion having a support surface supporting the arm holder from below thereof; and a first engagement portion which is flexible and extending upward from the support surface in a direction intersecting the support surface, and wherein the arm holders each include: a holding portion which is placed on the support surface and holding the arm so as to allow to be turned around the axis; a second engagement portion which is integrally formed on the holding portion so as to be protruded therefrom and which is engaged with the first engagement portion in a condition where the holding portion is inserted into the holder accommodation portion; and a fixed portion which is integrally formed on the holding portion so as to be protruded therefrom and which is installed on the holder support portion by fastening the bolt to the casing. a holding portion which is placed on the support surface and holding the arm so as to allow to be turned around the axis; a second engagement portion which is integrally formed on the holding portion so as to be protruded therefrom and which is engaged with the first engagement portion in a condition where the holding portion is inserted into the holder accommodation portion; and a fixed portion which is integrally formed on the holding portion so as to be protruded therefrom and which is installed on the holder support portion by fastening the bolt to the casing.