A bicycle saddle lifter is provided which is safe and simple in structure and which can raise the saddle of a bicycle while a bicycle driver is sitting on the saddle. The biasing force of a stroke spring 10 which biases the saddle upwardly is determined such that when the weight of a bicycle driver directly acts on the saddle, the saddle lowers, and when the driver applies force to pedals of the bicycle while sitting on the saddle, and the load on the saddle decreases, the saddle rises. While the driver is not sitting on the saddle, resistance resulting from the biasing force of the stroke spring prevents a ratchet pawl 13b for checking the ascent of the saddle from being disengaged from the corresponding ratchet gear 14 even by switchover operation. While the driver is sitting on the saddle, the biasing force of the stroke spring 10 is canceled by the load applied to the saddle and the resistance decreases, thereby allowing the ratchet pawl 13b for checking the ascent of the saddle to be disengaged from the ratchet gear 14 by switchover operation.