To improve attaching and detaching performance by providing a lock protrusion over which hook bodies may not easily climb after climbing over the inclined parts when the hook bodies are turned, and a fitting part to which the tip of a tool for turning a rigid plate is to be fitted.

Hook parts 22b, 22b of hook bodies 22, 22 are hooked on both ends of a rope positioned outside of a tire of a vehicular slip preventing tool mounted on the tire in a state where the hook bodies 22, 22 of a joint lock main body are extended. The tip of a tool is fitted to a fitting part 24 formed in the center part of a rigid plate 20 of the joint lock main body, the rigid plate 20 is rotated clockwise, and the hook bodies 22, 22 respectively climb over lock protrusions 23, 23, and the hook bodies are locked by lock protrusions 23, 23 after the hook parts 22b, 22b are contracted. Therefore, the rope is tightly stretched, and the tire can be mounted so that the vehicular slip preventing tool may not slip off. Therefore, the rope can be easily and tightly stretched with a simple structure.