A backup method, a backup apparatus, a program for executing a backup operation, and a recording medium for storing the program are disclosed for high-speed backup operations without any large-sized backup medium. The backup method backs up data stored in a first virtual recording medium into a backup medium under control of a virtual storage system. In the backup method, first, a second virtual recording medium is created to include a duplicate of only an actual data recording area, in which actual data are recorded, in a recording area of the first virtual recording medium. Then, backup data recorded in the second virtual recording medium are backed up into the backup medium.