A bottle stopper contains: a first connection part, a second connection part, an actuation member, an operation unit, a fitting sleeve, and a base. The first connection part includes two opposite cutouts. The second connection part includes an aperture. The actuation member includes an extension sheet, a post, and a threaded portion. The operation unit includes two projections and a drive element, wherein each of the two projections is a cuboid, and two distal ends of the drive element are connected with two eccentric positions of two outer surfaces of the two projections respectively. The fitting sleeve is hollow and is fitted on the post below a bottom of the second connection part. The base includes a screwing orifice for screwing with the threaded portion of the actuation member, and the fitting sleeve is fitted on the base.