Abstract: An anti-theft device has a substantially cylindrical body composed of two semi-cylindrical shells, and structure for hingedly connecting the shells with one another at one circumferential end so that the shells are turnable between an open position in which the other circumferential ends of the body are spaced from one another and a closed position in which the cylindrical body is arranged on a steering column and the other ends of the shells are locked with one another, the cylindrical body being formed so that it completely covers the ignition lock in the closed position so that an unauthorized person can not get access to the ignition lock, and structure for locking the other ends of the shells in the closed position.