PURPOSE: To rapidly, easily and effectively open or close a discharge opening, by providing a simple structure of the discharge opening at the bottom of a large size flexible container bag which can contain a large volume of contents.

CONSTITUTION: In a flexible container bag for automatic packing in which a discharge opening 3 having a smaller diameter than the bottom face is suspended at the bottom face 2 of a large size flexible container bag A having an opening 1 at the upper part. The upper part of the discharge opening 3 can be opened or closed by a one touch-shutter B. Freely and mutually detachable hooks 4a, 4b are equipped at both sides of the lower part and both sides of the bottom face 2. For the shutter B, fastening tools 6 are inserted in both ends of a string 5 fitted to the outer periphery of the discharge opening 3 or a clipper, which can be released by one-touch handling, holding the discharge opening 3 from the outside is attached thereto.