Abstract: In a wrapping connector driving apparatus for agricultural machines including a chain reeved around sprocket wheels on two shafts, a tension adjusting device is provided on the slack side of the chain. A tightener bearing against the chain tensions the chain. A piston slidably fitting in an oil enclosing cylinder is pressed against the tightener by a resilient member. An abnormal load, when acting on the chain, is absorbed by the resilient member and the oil enclosed in the cylinder, which is provided with a passageway for releasing the increased internal pressure due to the abnormal load. When relieved of the load, the cylinder can be supplied with oil by way of a check valve. The tension on the chain is thus automatically adjustable.