Bicycle rear derailleur

An apparatus for achieving the return of a chain 95 to a rear derailleur tension pulley 23 more easily by means of pedaling action when the chain 95 falls off from the tension pulley 23 is provided. The rear derailleur 97r is equipped with a base component 10, a link mechanism 11, a movable component 12, outer plate 20, inner plate 21, guide pulley 22, tension pulley 23, and chain return section 32. The base component 10 is a component which is mounted on the frame 102. The link mechanism 11 is a mechanism of which one end is mounted on the base component 10. The movable component 12 is a component which is mounted on the other end of the link mechanism 11, and which can be relatively displaced from the base component 10. The outer plate 20 is a component which is mounted on the movable component 12 so as to undulate like a see-saw. The inner plate 21 is a component which is installed so as to face the outer plate 20. The guide pulley 22 is a pulley which is mounted onto a portion on one edge of the plates 20, 21, between the plates 20, 21, so as to freely rotate and move in the axial direction, and which can be engaged with the chain 95. The tension pulley 23 is a pulley which can be engaged with the chain 95, and is mounted onto a portion on the other edge of the plates 20, 21, between the plates 20, 21, so as to freely rotate. The chain return section 32 is installed at a position on the inner plate 21 which is proximal to the position at which the tension pulley 23 is mounted, in a manner so that the clearance from the chain 95 at this position is narrower as compared to the clearance at other positions.