The present invention provides a generator for a bicycle which can be applied to a rim of all kinds of bicycle wheels, comprising: a rotating body 30 which is arranged to be adjacent to or to make contact with the rim 10, wherein eddy current induction magnet 35 is installed along an outer circumferential surface of the rotating body 30; a rotation shaft 62 whose one side end part is fixed at a center of the rotating body 30; and a generation unit 60 which is arranged at the other side end part of the rotation shaft 62, wherein at least a portion of the outer circumferential surface of the rotating body 30 is arranged farther outside than an outer circumferential surface of the eddy current induction magnet 35.