A storage system is characterized in that the storage system includes duplication-determination-unit determining means for determining a duplication determination unit, which is a unit to be used in determining duplications of data, on the basis of a duplication generation rate computed for each of a plurality of data division units obtained as a result of division of data stored in a storage device, and duplication eliminating means for carrying out processing to eliminate duplications of the data stored in the storage device on the basis of the duplication determination unit determined by the duplication-determination-unit determining means.