The invention relates to a closing device (1) for a container (2) with an opening (3). The device is characterized in that it has a sleeve part (5) that is sealingly placed on the inner wall (9) of the container and has a closing part (6) connected to said sleeve part closing the interior (10) of the container from the outside atmosphere. When inserted, the sleeve part extends from the closing part in the direction of the interior (4) of the container.
