PROBLEM TO BE SOLVED: To provide an inside plug of a chemical liquid storage container which is attached to a chemical liquid inlet and outlet opening of a storage container, in which a toxic or corrosive liquid chemical is stored, and which prevents the liquid chemical from leaking during preservation and transportation and also discharges the liquid chemical from the container safely and easily. SOLUTION: The inside plug 2 of a liquid chemical storage container closes a liquid chemical inlet and outlet opening 31 provided in a storage container 3 charged with a liquid chemical 33. A weakened part 24 is formed in the bottom side 23 of the plug 2 in such a manner that the thickness of the part 24 is 1-50% of the thickness of the bottom side 23 surrounding the part 24, whereby the part 24 can be pierced by a liquid chemical discharging pipe.
