Abstract: A wheel hub device includes a driving barrel and a hub shell mounted rotatably on an axle of a bicycle. When the shell is rotated via the barrel to move the bicycle forward, a coupling socket disposed in the shell threadedly engages the barrel and frictionally engages the shell. A coil spring is disposed between the shell and the coupling socket such that a sudden termination of rotation of the barrel while the bicycle continues to move forward due to inertia, imparts a frictional force to the coil spring to enable the coil spring to keep biasing against the coupling socket and against the biasing force of a associating spring disposed between the coupling socket and a sliding member, thereby disengaging the coupling socket from the shell to permit smooth idle rotation of the latter and to prevent rotation of the barrel with the shell.