BICYCLE HUB STRUCTURE

A bicycle hub has a hub member and a chain seat. The hub member has an open containing space and a central axis protruding from the containing space. The containing space has a linking ring around the central axis, and the linking ring further has an annular linking toothed portion. An end of the chain seat has an engaging portion with a circular stopper and a circular rib and a driving ring and a first engaging toothed ring. A second engaging toothed ring is installed onto the driving ring and engaging with the first engaging toothed ring, and a driving toothed portion is formed on an outer periphery of the driving ring. A spring is disposed between the top stopping portion and the driving ring, and two ends of the spring are respectively jacketed on to the engaging protrusion and the inserting protrusion.