PURPOSE: To obtain an installation device for an air-conditioner, capable of removing the casing of the same from an installation plate without employing any tool.

CONSTITUTION: An elastic part, positioned at the back surface of a casing 1 and having a thin part, is provided with a lower engaging unit and an installation plate 7 is also provided with a lower engaging unit while a finger hooking part is recessed at the fore end of the lower engaging unit. A groove type recess is provided at a connecting part between the back surface of the casing 1 and a bottom side 3 to facilitate the displacement of the lower engaging unit constituted on the bottom side 3. According to this method, the lower engaging unit of the casing 1 can be released from the lower engaging unit of the installation plate 7 through the thin part, the finger hooking part, the bottom side 3 of the casing 1 or the bottom side of a front panel without employing any tool. Accordingly, the removing of the air-conditioner casing from a wall is facilitated.