PURPOSE: To provide a connecting tool with locking mechanism which is about the same in shape as a chain ring to compose a chain, and assembled with the chain to produce convenient use.

CONSTITUTION: A connecting tool with locking mechanism is composed of a main body 1 to form an opened part 2; an opening and closing member 3 whose base end is pivotally mounted at the end of the main body for opening and closing the opened part; and a locking mechanism 4 which is arranged so as to be movable from the main body to the opening and closing member. The locking mechanism engages and disengages a plurality of its locking rings 6 on locking steps 7 provided in the opening and closing member in a state where the locking rings 6 are at each closing position.