A timing adjustment mechanism in a wrapping connector driving device includes a first pulley fixedly mounted on a first revolving shaft; a second pulley fixedly mounted on a second revolving shaft, the second pulley tightly fitting on the second shaft and being seated on an end surface of the second shaft; an intermediary wrapping connector wound on the first and second pulleys and extending therebetween; an idle pulley lever swingable about the axis of rotation of the second revolving shaft; a first idle pulley disposed near the second pulley on the tension side of the intermediary wrapping connector and rotatably secured to one end of said pulley holding lever; and an idle pulley rotatably secured to the other end of said pulley holding lever near said second pulley on the slack side of said intermediary wrapping connector, wherein all of the central portions of swing of the first and second pulleys, the tension and slack side pulleys and the pulley holding lever lie in the same plane.