The present invention includes an inner holder, an outer can, a first check valve and a second check valve. The inner holder includes a storage space. The outer can includes a slidable variable space for the inner holder to slide therein and an air channel for the slidable variable space to communicate with an exterior. The inner holder includes an air hole for the storage space to communicate with the slidable variable space. The first check valve is provided on the air hole and has an airflow direction towards the slidable variable space. The second check valve is provided on the air channel and has an airflow direction towards the exterior. The outer can is slidably moved outwards relative to the inner holder to suck out the air in the storage space and then slidably moved inwards relative to the inner holder to discharge air to the exterior.