Abstract: A sealing device for a vacuum air opening (10) of a dust bag or other dust collecting container (5) for a vacuum cleaner, has an elastic membrane (1) deflected and centrally fixed in a vacuum air opening tube (4) by means of a fixing element (2). Deflection of the flexible membrane (1) produces forces acting upon a partspherical surface (7) of the vacuum air opening tube (4), sufficient enough to ensure tight sealing of the vacuum air opening (10) and preventing any spillage of dust through the opening (10). The elastic membrane (1) is protected by a dome (3) with an opening (6) for vacuum air flow. Alternatively the membrane (1) may be mounted on a stem element (9) extending from the dome (3).