A mounting bracket is mounted on the vehicle and has a plurality of teeth displayed in an arcuate path about a pivot. The mounting bracket also has a vertically extending guide slot interposed between the pivot and the teeth. An arm is mounted on the pivot and has teeth thereon engageable with the teeth of the mounting bracket to lock the arm against pivotal movement. The arm also has a guide slot extending radially with respect to the pivot. A guide loop having the belt slidable therethrough is connected to a guide pin which is slidably guided in both the vertical guide slot of the mounting bracket and the radial slot of the arm so that pivotal movement of the arm about the pivot moves the guide loop vertically along the vertical guide slot of the mounting bracket to adjust the height of the shoulder belt. A spring washer surrounds the pivot and acts between the arm and the mounting bracket to urge the arm relative the mounting bracket to a normal position in which the teeth of the arm lock into engagement with the teeth of the mounting bracket.