Abstract: A differential locking mechanism for a final reduction gear is disclosed. Sleeve-like shaft support portions are formed fixedly at both sides of a differential case in a differential carrier and rotatably supported by the differential carrier. Rotating side gear shafts are connected to the side gears in the differential case and extend through the shaft support portions of the differential case to the outside of the differential carrier. The locking mechanism has a case independent of the differential carrier fixed to the outer side portion of the differential carrier to define an auxiliary chamber. A cylindrical intermediate shaft is mounted to an outer circumference of the rotating side gear shaft on the auxiliary chamber side in such a manner as to be coaxial with the rotating side gear shaft. One end of the intermediate shaft is connected to an inner circumference of the shaft support portion of the differential case so as to rotate therewith, while the other end is positioned in the auxiliary chamber.