The invention relates to a shut-off device comprising a housing which is to be connected to an adjacent conduit in a pressure-tight manner. A tubular passage is defined, in the housing, for a medium flowing through the conduit. Said device also comprises a sealing body which can be displaced by an articulated mechanism, by means of an adjusting drive that can be moved vertically in relation to the direction of flow, from an open position into a closed position in which the sealing contour of the at least one sealing body comes into contact with the tubular passage in a radially sealing manner. The articulated mechanism is guided parallel to the direction of displacement of the adjusting drive and comprises a bearing body to which the at least one sealing body is pivotably applied. The inventive shut-off device is characterised in that the bearing body comprises two diametrically opposed ribs and two corresponding grooves are formed in the wall of the housing or in an insert at least partially lining the housing, the ribs forming a span extending transversally to the direction of flow of the medium.