A deflector is arranged to prevent differential oil, as lubrication oil, leaking from a gap between a rod of an axle and a shaft portion of a drive shaft and passing through a unit bearing, from attaching to an inner periphery of a brake drum. A guide groove unit is formed on an inward surface of a hub in a vehicle-width direction so as to guide the differential oil leaking into an internal space defined inside of the deflector to outside of the brake drum.