A storage system comprising: a storage device for storing division data configuring a file and also storing address data based on a data content and storage location of a reference destination, the address data referring to the division data or other address data; and a data storage controlling unit for, in a case that the division data or the other address data is to be newly stored into the storage device, and the division data or the other address data to be newly stored has a same data content as data already stored in the storage device, controlling to refer to the data already stored in the storage device as the division data or the other address data to be newly stored, by using the address data, wherein the data storage controlling unit includes an address data acquiring unit for accepting file specification information that specifies a copy target file stored in the storage device and acquiring the address data of the copy target file based on the file specification information, and an address data set-up unit for setting up the acquired address data in the storage device so that the copy target file is stored in a copy destination directory, wherein the storage device is configured to store file management structure data storing a plurality of address data referring to a plurality of the division data configuring the file and also store directory management structure data storing address data referring to the file management structure data and specifying a directory that is a storage location of the file stored in a reference destination of the address data; the address data acquiring unit is configured to specify the file management structure data storing address data referring to division data configuring the copy target file based on the file specification information, and acquire address data referring to the file management structure data; and the address data set-up unit is configured to copy the address data acquired by the address data acquiring unit into the directory management structure data specifying a directory located in a copy destination of the copy target file, wherein the storage device is configured to store a correspondence map that makes an identifier given to the each file correspond to address data of the file management structure data referring to the file, and also store the identifier given to the file referred to by the address data, as the address data referring to the file management structure data in the directory management structure data; and the data storage controlling unit is configured to refer to the file based on the identifier stored as the address data in the directory management structure data and based on the correspondence map. a storage device for storing division data configuring a file and also storing address data based on a data content and storage location of a reference destination, the address data referring to the division data or other address data; and a data storage controlling unit for, in a case that the division data or the other address data is to be newly stored into the storage device, and the division data or the other address data to be newly stored has a same data content as data already stored in the storage device, controlling to refer to the data already stored in the storage device as the division data or the other address data to be newly stored, by using the address data, wherein the data storage controlling unit includes an address data acquiring unit for accepting file specification information that specifies a copy target file stored in the storage device and acquiring the address data of the copy target file based on the file specification information, and an address data set-up unit for setting up the acquired address data in the storage device so that the copy target file is stored in a copy destination directory, wherein the storage device is configured to store file management structure data storing a plurality of address data referring to a plurality of the division data configuring the file and also store directory management structure data storing address data referring to the file management structure data and specifying a directory that is a storage location of the file stored in a reference destination of the address data; the address data acquiring unit is configured to specify the file management structure data storing address data referring to division data configuring the copy target file based on the file specification information, and acquire address data referring to the file management structure data; and the address data set-up unit is configured to copy the address data acquired by the address data acquiring unit into the directory management structure data specifying a directory located in a copy destination of the copy target file, wherein the storage device is configured to store a correspondence map that makes an identifier given to the each file correspond to address data of the file management structure data referring to the file, and also store the identifier given to the file referred to by the address data, as the address data referring to the file management structure data in the directory management structure data; and the data storage controlling unit is configured to refer to the file based on the identifier stored as the address data in the directory management structure data and based on the correspondence map.