To permit an appearance difference between the attachment condition and the separation condition to be clearly recognized in a stopper of a beverage container which improves cleanability by separating and disassembling the stopper body.

An inner stopper part 19 is provided removably from below an outer stopper part 18. To fix the inner stopper part 19 to the outer stopper part 18, the inner stopper part 19 includes engagingly stopping members 33 and the upper opening 20 of the outer stopper part 18 includes engagingly stopping receiving parts 28. The engagingly stopping members 33 of the inner stopper part 19 are provided to get exposed upward from the upper opening 20 of the outer stopper part 18 and detachably engagingly stop there. An inward collar 29 and a lower outward collar 32 permits the inner stopper part 19 to be positioned when it is inserted into the outer stopper part 18 from below. Engagingly stopping an upper outward collar 27 to the upper part of engagingly stopping receiving parts 28 permits the inner stopper part 19 to be prevented from coming off. Consequently, removing the inner stopper part 19 from the outer stopper part 18 enables each part of the stopper to be cleaned. The sure attachment of the inner stopper part 19 to the outer stopper part 18 can be visually confirmed from the outside of the stopper body 9.