A sealing member for reducing or preventing loss of air from a multi-cyclone dust separating apparatus in a vacuum cleaner is provided. A sealing member comprises an inner sealing portion for maintaining sealing between a first cyclone unit and second cyclone units, an outer sealing portion for reducing or preventing the inflow of air to the cyclone dust separating apparatus from its exterior, and a cyclone receiving portion connected to the inner and outer sealing portions by a connecting member. The cyclone receiving portion includes holes in which at least portions of the second cyclone units are respectively received.