PURPOSE: To reduce the dimension of a connector, equipped with a locking mechanism, in its width by locating a lock lever mounted on the connector in a position inside the rocking arm of a jack, and allowing the pawl parts to rotate in the direction to approach each other.

CONSTITUTION: The cover 21 of a plug connector 11 is provided at the side wall 21a with a groove 21d to fix the foremost extremity of a lock lever 22, which is inserted and a tab 21c by a key-shaped slit 21b. Another tab 22a protruding inside and outside and a hook 22b are furnished on the lever 22 made from a spring leaf while a rocking arm 25a having a detention part 25a' in the form of a square hole is installed on a jack connector 25, and these parts are put together for assembling. Thereby the free end of the tab 21c contacts the lock lever 22, and the protruding curvature is pressed to cause the lever 22 to deform, and the hook 22b is engaged by the detention part 25a', and thereby the two connector members are connected together and locked or then disengaged. This enables reducing the outside dimensions and enhancing the producibility.