To easily and surely connect the end parts of copings to each other, and prevent the connection from being influenced by the expansion and contraction of the coping.

One coping 2 having locking pieces 1 formed so as to be bent upward on the inner surface side near both lateral lower ends thereof is set in a prescribed position in the state where both lateral lower end parts of a draining joint material 3 are engagingly locked by the locking pieces 1 and housed therein, and the other coping 2 having locking pieces formed so as to be bent upward on the inner surface side near both lateral lower ends thereof similar to the one coping 2 is set in a prescribed position. The draining joint material 3 is slid on the other coping 2 side, and both the lateral lower end parts are engagingly locked by the locking pieces 1 of the other coping 2, whereby both the copings 2 are mutually connected.