To provide a bicycle equipped with an auxiliary driving force, capable of centralizing the components of an auxiliary driving force system for compact formation, and improving the weight balance and appearance of the bicycle.

A bicycle equipped with an auxiliary driving force is constructed by incorporating an electric motor 10, a reduction gear 14, a battery 12 and an electromagnetic clutch, a pedal pressing force sensor and a control unit 13 in a general bicycle. The pedal pressing force sensor is installed in the bearing portion of a pedal crankshaft 2, and the battery 12 is disposed below a saddle 17 in the rear side of a seat frame 16. The electric motor 10 imparting auxiliary driving force includes a motor shaft extended to the front of the pedal crankshaft 2 in a direction orthogonal to the same. The motor shaft is connected to the reduction gear 14 disposed between the electric motor 10 and the pedal crankshaft 2, and the electric motor 10 and the reduction gear 14 are disposed along a front frame 18. A numeral 15 denotes an auxiliary driving force variable volume set in a handle portion.