The utility model provides the composite rear hub device of a bicycle, comprising an axle, an axle body, an axle bowls, and an axle bumper. A sliding ball block is provided between the axle bowl on one side and a ball bowl, and a flywheel is supported on the axle by the sliding ball block and the ball bowl which are on the two ends of the flywheel. The composite rear hub device of the utility model can adjust the axial assembly clearance on any side of the axle to bring convenience to the assembly and maintenance of the bicycle; besides, the device of the utility model can reduce the diameter and the number of gear of the flywheel, which is favorable for improving the transmission ratio of the bicycle.