String vibration is reduced without causing friction loss. A silent chain is comprised of a multiple number of link plates, each of which has a pair of tooth portions and pin holes and which are laminated laterally and longitudinally and guide plates which are arranged at outermost positions of the link plates. The link plates and the guide plates are connected by connecting pins. In this construction, some of the guide plates are made heavier than that of other guide plates and are irregularly mixed in a longitudinal direction of the chain. Thus, the natural frequency can be changed in an arbitrary chain span and string vibration may be reduced without causing friction loss.