Abstract: A cable tension device includes a fixing seat, a rotation shaft, a ratchet unit, a movable seat, a safety locking plate, a control member, an engaging board, a push board, a compression spring, and a tension adjustment knob. Thus, when the cable is tightened to a determined extent by rotation of the movable seat, the force applied by the cable on the ratchet unit is greater than that applied by the engaging board and the push board on the ratchet unit, so that the engaging board is pushed and deflected by the ratchet unit to pass by the ratchet unit, and the movable seat performs an idle rotation, thereby preventing the cable from being tightened too excessively.