A hub module includes an axle member, a hub shell mounted on the axle member, at least two sprocket carriers, and a pair of end caps respectively secured to opposite ends of the axle member. Each of the sprocket carriers includes a carrier body having an outer profile, and a bearing unit mounted in the carrier body. The outer profiles of the carrier bodies of the sprocket carriers are different from each other. The bearing units of the sprocket carriers are the same in total length and inner diameter. Any one of the sprocket carriers is able to be mounted on a carrier-mounting section of the axle member and cooperates with the axle member and the hub shell to serve as a hub assembly.