To provide a power-assisted bicycle which makes a rider safely ride on even if it becomes necessary to turn a steering wheel sharply during the middle of drive.

The power-assisted bicycle assists the power of pedaling by a motor 40 driven by a battery 41 as a power source. The head tube of a frame is fitted with a steering angle detector 60. A controller 50 controlling the motor 40 performs control for weakening an assist force by the motor 40 when the steering angle detected by the steering angle detector 60 exceeds a prescribed value.