A bicycle hub includes a housing, in which a first ratchet device, a second ratchet device, and an elastic device are received. The first ratchet device is rotated freely in the housing, and the second ratchet device is fixed to the housing. The first ratchet device has a first ratchet portion, the second ratchet device has a second ratchet portion, and the elastic device urges the first ratchet portion to engage the second ratchet portion of the second ratchet device when the first ratchet device is rotated in a direction. A driving device is connected to the first ratchet device to rotate at an end of the housing while the first and the second ratchet portions are located at an opposite end of the housing.