An automatic binding device for coupling at least two containers includes a latch being twisted during insertion/disengagement into/from a coupling hole of corner castings; a pair of housings for covering a circumferential surface of a rotating shaft of the latch; and a torsion spring for re-rotating the latch substantially to its original condition before rotating, the torsion spring being installed at the circumferential surface of the rotating shaft. Furthermore, the automatic binding device for a container is provided with the indicator capable of allowing a user to see the present state of the binding device with the naked eye.