A foldable bicycle has a front frame, a main frame, a rear frame and a driving device. The front frame has a front fork device with a front fork and a front wheel rotatably connected to the front fork. The main frame is connected to the front frame and has a front arm, a connecting device and a rear arm. The front arm has a front pivot rod. The connecting device is pivotally connected to the front arm. The rear arm is pivotally connected to the connecting device and has a rear pivot rod. The rear frame is rotatably connected to the main frame and has a rear fork device with a rear fork and a rear wheel rotatably connected to the rear fork. The driving device is mounted on the main frame to drive the rear wheel to rotate relative to the main frame and the front frame.