Motor assisted bicycle

To provide an efficient assist by a motor by setting an assist amount based on fatigue information which is actually measured while estimating the degree of fatigue which a rider feels in a motor assisted bicycle. Means for Resolution In a motor assisted bicycle which includes: a stepping force sensor 2 which detects a stepping force generated on a pedal; an assist amount control part 10 which includes an assist amount correction means which performs the estimation of fatigue of a human body and decides an assist force corresponding to an output of the stepping force sensor 2; and a motor 5 which generates the assist force and assists a drive force, the motor assisted bicycle further comprises a vehicle speed sensor 1 which detects a vehicle speed of the vehicle, and the assist amount control part 10 includes: a basic assist amount setting part 11 which sets by calculation a basic assist amount based on the stepping force and the vehicle speed; and a fatigue level estimation part 12 which performs the increase/decrease correction of the basic assist amount by estimating a fatigue level of a rider.