Disclosed herein is an electrode terminal connecting device for electrically interconnecting two or more battery modules, including a conductive connecting member for electrically interconnecting electrode terminals of the battery modules, the conductive connecting member having two through-holes formed at positions corresponding to the distance between the electrode terminals, an insulative sheathing member for surrounding the conductive connecting member, a portion of an open rear of the insulative sheathing member being closed for easy installation of the conductive connecting member, the insulative sheathing member including a side wall protruding from the outer circumference of the conductive connecting member such that the side wall has a predetermined height, and an insulative cap connected to the top of the insulative sheathing member by a hinge structure for opening and closing an open front of the insulative sheathing member, the insulative cap having hollow buffers protruding from the inside thereof for surrounding portions of the electrode terminals protruding through the through-holes.