In a device (1) for pressing in slot sealing pieces (12, 14) for winding bars (20) inserted into the slots of a stator laminated core of an electric machine, a plunger (8) is arranged by means of a force-generating device (4) in a collet (2) with a cam (3). The plunger (8) and the cam (3) are situated opposite one another and move toward one another in the fashion of a screw clamp during operation of the force-generating device (4). In this arrangement, when slot sealing pieces are pressed in the cam (3) engages in an axial slit (11) of a first, upper prismatic body (12), and the plunger (8) acts on an end face (13) of a second, lower prismatic body (14). The device (1) for pressing in slot sealing pieces (12, 14) is arranged with lifting devices (22) on a support frame (23) which can be moved along the slot sealing pieces (12, 14) in the stator laminated core.