To provide an inner plug capable of easily and rapidly refilling a content.

The inner plug of a container includes a body portion 2a having a through-hole h connected to the inside of a container and fixedly held by the mouth portion 1a of the container 1, and a valve element 2b rockingly held in the through-hole h of the body portion 2a to close the through-hole h in the initial attitude. A small diameter hole h1 for spouting the content filling the container 1 is provided in the valve element 2b.