A differential device includes a differential casing 15 having a cylindrical part 3, first and second sidewalls 5, 7 formed on both sides of the cylindrical part 3 and a flange part 13 formed on the outer circumference of the first sidewall 5, a differential mechanism 23 having a differential member 17 to which a driving force is transmitted from the differential casing 15 and first and second output members 19, 21 both engaged with the differential member 17 to distribute the driving force, a diff lock mechanism 29 having a clutch member 25 rotatable integrally with the first sidewall 5 and connectable with the first output member 19 by a relative movement of the clutch member 25 to the first sidewall 5 in the axial direction of the cylindrical part 3 and an actuator 27 for moving the clutch member 25 in the axial direction of the cylindrical part 3 and a differential restraint mechanism 33 having a frictional clutch 31 arranged on the side of the second sidewall 7, for restraining a relative rotation of the differential casing 15 to the second output member 21.