With a push device for the axial insertion of an elongate, flexible body (8, 10), in particular of a flexible tube, a cable or similar elements into a sheath, and axial force introduction unit (19, 20, 47, 49) is provided, which by way of a non-positive fit or a positive fit, applies a push movement onto the elongate body and is arranged in a stationary manner relative to the sheath (2) or is guided on a predefined movement path.