On the outer peripheral surface of a steering column (2b), a protruding wall section (17) is provided in the periphery of a locking through-hole (11a), a recessed groove (20) that engages with the protruding wall section (17) is provided in the area surrounding a guide section (13a) of the abutment surface (19) of a lock unit (12a), and said protruding wall section (17) and recessed groove (20) engage; preferably, a recessed section (18) provided in the steering column (2b) and a protruding section (21) provided on the lock unit (12a) are fitted together, and by supporting and fixing the lock unit (12a) against the steering column (2b), the steering column (2b) is saved from damage such as cracking even when a large force is applied to try to rotate the steering wheel in a state in which the ignition key is turned to OFF.