The present invention provides a generator for a bicycle capable of improve the generation efficiency. The generator comprises a support body; a rotary body arranged to rotate relative to the center of the axis of the support body and inputted from the exterior; a coil supported by the support body; a yoke supported by the support body; and first and second magnets capable of rotating with the rotary body around the center of the axis. The yoke includes a magnet relative portion arranged between the first magnet and the second magnet.