A bicycle gearshift system is mounted on the rear part of the frame of the bicycle. The bicycle gearshift system includes an electrically powered rear derailleur, a rear hub, a charger part, and a gearshift control part. The electrically powered rear derailleur is mounted on the rear part of the frame. The rear hub is also mounted to the rear part of the frame. The rear hub has an electrical generator mechanism that generates electricity through the rotation of the wheel. The charger part is mounted on the rear hub and stores the electrical energy that was generated by the generator part. The gearshift control part is equipped on the electrically powered rear derailleur, where gearshift control of the electrically powered rear derailleur is performed through the energy that is stored in the charger part.