A bicycle controlling device including a lifting controller, a shifting controller, a height adjusting assembly, an electric rear derailleur and a seat height controller is disclosed. The lifting controller and the shifting controller are respectively adapted to generate and emit a lifting control signal or a shifting control signal. The height adjusting assembly is positioned in the seat tube and can be controllably lifted or fixed at a height. The seat height controller is fixed to the seat tube, and includes a wireless signal receiver, a control circuit and a motor. The wireless signal receiver is adapted to receive/transmit the lifting/shifting control signal to the control circuit, which is electrically connected with the electric rear derailleur and the motor, and controls the motor/the electric rear derailleur with the received lifting/shifting control signal. The motor can mechanically control the lifting of the height adjusting assembly or fix its height.