Deduplicated backup data of a plurality of generations are aggregated and stored.A storage apparatus is connected via a network to a host system making a content write request and includes a storage unit providing one or more containers composed of a specified storage area, and a back up unit storing the content in the container in accordance with a backup request from the host system; and wherein the backup unit cuts out the content into one or more chunks, detects a duplicate chunk, which is a duplicate of a chunk stored in the container, from the cutout chunks, and additionally writes the chunk, other than the duplicate chunk, to the container where the duplicate chunk is stored.