PROBLEM TO BE SOLVED: To provide a plug structure of an infusion container capable of exactly sealing an infusion, enhancing production efficiency, and suppressing cost.SOLUTION: A tightly sealing means 15 for keeping a sealed infusion bottle 2 includes an inner plug member 16 which can be elastically deformed, an outer plug body 17 which presses the inner plug member 16 against a mouth 3 so as to be elastically deformed, and locking mechanisms 18 which are provided at the mouth 3 and the outer plug body 17, permits the motion of the outer plug body 17 in the plug-closing direction, and regulate the motion in the plug-opening direction. The outer plug body 17 is locked by the locking mechanism 18 to keep the elastically deformed state of the inner plug member 16 so that a space between the upper end 3a of the mouth 3 and the inner plug member 16 is sealed.
