PURPOSE: To shorten an access time to data by stocking plural media in an autoloader, sending succeedingly it to a deck and reading and writing it continuously.

CONSTITUTION: A medium 5 in a warehouse 3 is taken out from a housing shelf 2 by an accessor 5 and sent to an unused medium stock part of an autoloader 6. At this time, the medium is loaded into a deck 4 by a medium loading part when the deck 4 is empty and the data is read. The medium to be read next is taken out from the housing shelf 2 by the accessor 5 and sent into the unused medium stock part and stored. The former medium is ejected from the deck 4 and entered into a used medium stock part when the former medium is ended to be read. The medium to be read next is loaded into the deck 4 by the medium loading part when the deck 4 is empty and the data is read. That is, the access time to the data is shortened since the device is constituted so that plural media are stocked temporarily by the loader 6 and the medium is loaded into the deck 4 continuously.