To provide an attachment that can be mounted easily for relaxing and eliminating the uncomfortable odor of blow-off air of an already installed air-conditioner and returning clean or fragrant air into a room.

An attachment 1 is composed of a cover member 2 that covers a blast opening B of an air-conditioner A and has an uncomfortable odor prevention ventilation filter 13 on a reverse side and flat members 7 and 8 that are pivoted at the upper and lower edges of the cover member 2 so that they can be raised and rotated and are removably mounted to the upper and lower parts of the periphery edge of a blast opening B of the airconditioner A. Then, by mounting the cover member 2 of the attachment 1 to the front side of the blast opening B of the air-conditioner A, a blow-off air from the blast opening B of the air-conditioner A passes through the high-ventilation filter 13 and is discharged into air.