To provide the bicycle which permits it to be properly assisted by power by a simple constitution when it is in use.

This bicycle is equipped with a bicycle main body 2 which applies driving force to a front wheel 2a or a rear wheel 2b based on the rotation of a pedal 2d, a motor 5 which is mounted onto the bicycle main body 2 to give torque to the front wheel 2a or the rear wheel 2b, a bicycle speed sensor 3 detecting the wheel speed of the front wheel 2a or the rear wheel 2b to which the torque of the motor 5 is given, and with a controller 4 which controls the motor 5 based on the detected signal of the bicycle speed sensor 3. And it is so constituted that the aforesaid controller 4 starts sending driving current to the motor at the speed set in advance in the range of low bicycle speeds, and quickly increases driving current as the bicycle speed is increase, after driving current has come up to its peak value, driving current is so controlled as to be gradually decreased as the bicycle speed is increased, and driving current is so controlled as to be suspended at the speed higher than the speed set in advance in the range of high bicycle speeds.