To perform rapid opening and closing of a coupling ring and to provide a coupling ring to be manufactured at a low cost.

A coupling ring is formed in such a manner that the base end of an opening closing lever 2 is pivotally mounted on one end of the opening part of a C-shaped lever 1, and the opening part is openable by rotating for opening and closing through rotation of the opening closing lever 2. In this case, a lock lever 3 to block release rotation to the inside of the opening closing lever 2 is disposed in such a state to span between the opening closing lever 2 and a position where the C-shaped lever 1 is positioned facing the opening closing lever 2. At least one end of the lock lever 3 is pivotally mounted on the opening closing lever 2 or the C-shaped lever 1 and brought into a releasable and rotatable state. Further, the other end is removably locked to the C-shaped lever 1 or the opening and closing lever 2.