PURPOSE: A saddle height controlling device of a bicycle is provided to improve the safety and the convenience for a passenger by controlling the height of a saddle of a bicycle according to the running condition during the driving of the bicycle. CONSTITUTION: A saddle height controlling device of a bicycle comprises the following: a saddle ascending and descending unit(200) controlling the height of a saddle(23) by moving the saddle upward and downward; and a control unit(300) controlling the saddle ascending and descending operation. The saddle ascending and descending unit comprises the following: a motor member generating the torque; an elevating body member(17) connected to the saddle; an operation member moving the elevating body member; and a torque transfer member transferring the torque of the motor member to the operation member. The operation member includes a screw combined to the elevating body member.
