For a less load to a shutter and secure motions of the shutter without damaging a ferrule, a rear stopper guide (22) and an intermediate spring guide (23) covering an upper side of a hold of an optical plug, and an outer cover (24) covering a front outer periphery of the hold are provided; the outer cover (24) is pushed by an optical connector adapter (Q) to move from a front end position of the hold to a rear end position, an inner side of the outer cover (24) is provided with a shutter (21) which can be swung from a lid close position to a lid open position, and the shutter (21) is automatically opened and closed by a shutter automatic opening and closing mechanism (S) in accordance with a rack and pinion system, working with rearward and forward movements of the outer cover (24).