An optical transmission line connecting device includes a mechanical splice capable of connecting a pair of optical fibers to each other; a pair of holders capable of respectively holding a pair of fiber housing members; a splice support section capable of supporting the mechanical splice at a predetermined location; a pair of holder support sections capable of respectively supporting the holders at respective predetermined locations; and a pair of deflector sections capable of deflecting intermediate portions of end lengths of a pair of covered optical fibers within a predetermined deflection range in a pre-connection state, the intermediate portions extending between the mechanical splice and the holders. Each deflector section includes a first shiftable member capable of shifting between an operative position where the first shiftable member contacts an intermediate portion of each of the covered optical fibers and causes a minimum deflection within the deflection range in the intermediate portion, and an inoperative position where the first shiftable member does not contact the intermediate portion.
