To provide a connecting tool with a lock exhibiting good operatability even under a condition where a glove is worn and wherein opening of a ring is enlarged.

A lock structure 8 having continuously arranged umbrella-shaped pieces is provided and a connection ring 3 is formed by a fixed arm 4 fixed on the end part of a main body part 2 having a connecting part 9 of a code formed thereon and a movable arm 5 and a part of a ring structure of the connecting ring 3 is opened by rotating the movable arm 5 by means of an opening lever 6 formed on the movable arm 5. The opening of the ring structure by means of the movable arm 5 can be locked by means of the lock structure 8 provided on the main body part 2. Therefore, it can be used as a cord lock for preventing a theft from occurring by connecting a flexible cord with the connecting part 9 and it exhibits high value for use as a flow stopper for a snow board and skis.