Problem to be Solved: To provide a system capable of stably supplying power to electrical components of a bicycle. Solution: An auxiliary power supply system 100 includes an auxiliary power supply portion 200. The auxiliary power supply circuit 200 is operated by power from a power generating portion 10a provided in the bicycle. The auxiliary power supply portion 200 supplies power generated by the power generating portion 10a to electrical components 20 mountable to the bicycle depending on a supply situation of power from a power supply 14 mounted on the bicycle.
