A rear derailleur for a bicycle includes a base member for attaching the rear derailleur to the bicycle, a movable member for supporting a chain guide, and a linkage mechanism coupling the base member to the movable member so that the movable member is capable of movement relative to the base member. An electrically operated actuating member is operatively coupled to the linkage mechanism, wherein moving the actuating member in a first direction causes the movable member to move laterally toward a rear wheel of the bicycle, and moving the actuating member in a second direction causes the movable member to move laterally away from the rear wheel of the bicycle. A power storing mechanism is disposed in a power transmission path between the actuating member and the movable member for storing relative forces applied between the actuating member and the movable member.