A compact and light weight axle unit with good durability and reliability for driving a vehicle wheel is provided wherein the splined bore 28 of the hub 6a is engaged with the splined shaft 30 of the drive shaft member 29, and a stop ring 35 is held between the outer engagement groove 25 on the inner peripheral surface of the splined bore 28 and the inner engagement groove 24 on the outer peripheral surface of the splined shaft 30 to prevent the splined shaft 30 from being removed.