A sealing device for sealing at least one underpressure or overpressure zone adjoining a surface which is moved in a movement direction in a paper, tissue or cardboard machine, includes at least one sealing element which is located opposite the moved surface and has at least one feed channel for a lubricant. In order to considerably decrease the wear of a sealing element uniformly over the entire length thereof, the at least one feed channel ends in a supply channel, which is arranged at the beginning of the sealing element in the movement direction.