A bicycle rear derailleur has a mounting base, a moveable base, and a friction assembly. The moveable base has an axle. The friction assembly is mounted in the moveable base and has a driving disk, a driven disk, multiple rotating members, and a friction member. The driving disk is connected with the axle in a non-rotatable manner. The driven disk is rotatably and axially moveably mounted in the moveable base. Each disk has multiple curved rotating member guiding recesses. Each rotating member guiding recess of the driving disk has a depth decreased along a first rotating direction. Each rotating member guiding recess of the driven disk has a depth decreased along a second rotating direction. The rotating members are mounted respectively in the rotating member guiding recesses. The friction member is mounted in the moveable base in a non-rotatable manner and abuts the driven disk.