Abstract: The invention relates to a stacker for flat objects, in which a conveyor moves the objects to be stacked in in an edgewise manner. A drum rotates permanently in front of the orifice of a hollow cylindrical body, connected to a suction source. The stack of already stacked objects is engaged against said drum. A shell, controlled in rotation, controls the application of suction through the openings of the drum, of an object inserted between the drum and the stack. Suction application is timed to correspond to a displacement of the leading edge of the object inserted between the orifice and the stopping border of the receptacle. Application to postal sorting.