A device for blocking the steering shaft of a motor vehicle against rotation by a locking bolt which can be axially moved back and forth between locked and released positions via a two-directionally rotatable control member, and comprises a locking element and an actuating element. The control member surrounds the actuating element and has two helically extending interior grooves and a planar end surface adjoining the grooves and extending perpendicular to the axis of rotation of the control member. A transverse pin axially displaced in the actuating element cooperates with the grooves and the end surface. A helical compression spring is supported on the actuating element via a plunger having an oblong hole through which the transverse pin extends, and which plunger can be axially displaced in the actuating element by a stop so that the helical compression spring presses the transverse pin against the end surface via the locking element and the actuating element in the released position of the locking bolt.