A green bike comprises a frame, two wheels, a first internal-gear module and a second internal-gear module and a transmission element. The frame has a pedal, a front supporting unit, a rear supporting unit, and a seat unit. The two wheels are attached to the front supporting unit and the rear supporting unit, respectively. The transmission element is disposed in the frame or a tube shield linking to the frame. The first internal-gear module and the second internal-gear module are coupled with the pedal and at least one of the wheels. The transmission element links the first and the second internal-gear modules for delivering power to the at least one of the wheels.