PURPOSE: To shorten the handling time by providing a second storage means, where plural commutative storage mediums where idle sections are reserved can be stored, in the vicinity of a commutative storage device which reads and writes data from and in the commutative storage mediums.

CONSTITUTION: The storage medium remaining in a deck 1 is taken out of the deck 1 and is stored in an idle cell 3a in a local cell 3. It is moved to a storage cell 3b of the local cell 3 where a requested storage medium is stored. The requested storage medium is taken out of the storage cell 3b and is loaded to the deck 1. This operation is successively executed by the indication of a controller 5. In this case, the extent of movement of an accessor 4 is very short because the requested storage medium exists in the local cell 3. Thus, the handling time is considerably shortened when the requested storage medium exists in the local cell 3.