PURPOSE: To facilitate mounting and demounting and positioning of a rim wheel by forming a guide rib on the outside of a rim-wheel fitting stage in correspondence with a hub bolt hole, on a rear axle wheel hub which is used for a large- sized truck.

CONSTITUTION: A wheel hub 10 is rotatably arranged onto the outside of an axle pipe 18 through bearings 19 and 20 and screwed onto the flange 21 of a rear-axle driving shaft 17 which is arranged rotatably in the axle pipe 18. The wheel hub 10 transmits the motive power of the above-described shaft 17 to a rim wheel 15 having double tires 26 and 27 installed. In the above-described constitution, a guide rib 13 is formed on the outside of a fitting stage corresponding to a hub bolt hole 16 on the rim wheel 15. Therefore, mounting and demounting of the rim wheel 15 onto the wheel hub 10 are facilitate, and positioning of the rim wheel 15 can be performed simply and accurately.