PURPOSE: To provide a bicycle transmission having a compact size, light weight and high durability, and allowing an easy and proper gear change operation.

CONSTITUTION: A carrier 19 is fixed to one end of a crankshaft 13, and a plurality of planetary gears 21 integrated with gears having a different number of teeth are pivotally provided along the same circumference as the carrier 19 in such a way as freely rotatable. A driven rotor 7 integrated with a sun gear 8 and a cylinder penetrating the inside of a hanger is laid inside the planetary gears 21 for engagement with one element thereof. A sprocket 9 is fixed to the other end of the rotor 7. Also, a plurality of inner gears 23 and 24 for engagement with the planetary gears 21 are laid at the outer side thereof in such a way as independently rotatable. In addition, a gear case 26 enclosing the external surface of the gears 23 and 24 are fixed to a bicycle frame, and one-way clutches C2 are laid in the space between the inner gears 23 and 24, and the gear case 26, and constitution is so made as to allow the selection of one of the clutches C2 for engagement.