PURPOSE: To improve the ease of work and the finish of mounting by providing a first attaching part at the top of the mounting plate, a second attaching part on the inboard side of the first attaching part and a hole on the back of the air conditioner that engages the second attaching part.

CONSTITUTION: After fitting a mounting plate 1 to the wall with screws, a room unit 5 is moved to the wall so that a first attaching part 2 of the mounting plate 1 may be positioned at its retaining part. In the course of this procedure, a projection of a second attaching part 4 of the mounting plate 1 engages with a hole in the room unit 5. This completes the temporary fixing of the room unit 5, and the tightening of screws will complete the installation. Therefore, since the engagement between the projection of the first attaching part 2 and the stepped part of the room unit 5 prevents the unit from dropping under the temporary fixing condition of the room unit 5, both hands can be used for other works, which improves workability. Further, there will be no leaning forward of the central part of the room unit 5, and so, the finish of the installation can be improved.