To improve handling of a cap body and also to stabilize assembly of an inner plug with a container in an outer cap assembled with the inner plug having an ejection cylinder with a function for preventing illegal unsealing, by rigidly holding tight assembly of the inner plug with the container and by opening/closing the inner plug at the body where the inner plug is attached to/removed from the body.

The cap structure comprises an inner plug 5 which is tightly assembled with a mouth cylinder 2 of a container 1 and has a standing ejection cylinder 9 and an outer cap 13 wherein a body 16 to be attached to/removed from the ejection cylinder 9 is integrally coupled with a pressing board 15 connected with an assembly cylinder 14 to be assembled with the mouth cylinder 2 so that it cannot be removed via a separating piece 17 which is easy to break. In this case, assembly of the inner plug 1 with the container 1 is held by the pressing board 15, and the separating piece 17 is positioned at a diameter size position of the body 16.