A joint-disconnecting tool includes a clamp and a controller. The clamp includes a case, two branches, a pin and two linking elements. Each of the branches includes a lever extending in the case and a jaw extending out of the case. The pin connects the levers to the case. Each of the linking elements includes an end pivotally connected to one of the levers in the case. The controller includes two handles, a wire, a sheath and a spring. The handles are pivotally connected to each other. The wire includes an end connected to one of the handles and another end connected to another end of each of the linking elements. The sheath wraps the wire except for the ends. The sheath includes an end abutted against another one of the handles and another end abutted against the case. The spring tends to push the linking elements from the case.