PURPOSE: To prevent liquid remaining in a bag from spilling and easily re-seal a bag by providing a plug which can be inserted into an opening of a tube wherein the opening is formed with an end of the tube cut off.

CONSTITUTION: A tube 1 for dispensing liquid with an end closed is attached to a bag made of a plastic film, liquid is filled from an opening 2a of the plastic film, and after filling the opening 2a is sealed by heat-adhesion or an adhesive agent. When sealed liquid is to be dispensed, the tube 2 attached to the bag is cut off at a cut line 4 by using scissors or the like. When the liquid is dispensed, the opening 2a of the tube 2 serves as a dispensing port, so that the port is stable and the liquid may not splash. When re-sealing the bag, a cut-off plug 3 is inserted reversely into the opening 2a of the tube 2 formed with an end of the tube 2 cut off for tightly closing, thereby simplifying resealing of the packing bag.