A filter unit that is used by being detachably mounted on a lens barrel constituting an imaging device is configured so as to include a discoidal filter body, an annular filter frame that receives the filter body, an adhesion film that is formed between the filter frame and the filter body and that is formed of an elastic adhesion, and a decorative annular frame received at a portion that is inside the filter frame and that is, when mounted on the lens barrel, on the imaging object side with respect to the filter body. The filter body and the filter frame are in noncontact with each other by forming the adhesion film between the filter frame and the filter body, and by disposing the decorative annular frame, the adhesion film is hidden under the appearance of the filter unit when the filter unit is mounted on the lens barrel.