PURPOSE: To transfer and copy data between disk drives at a high speed by controlling simultaneously the two flexible disk drives with one flexible disk controller.

CONSTITUTION: This information storage device is provided with one flexible disk controller 13 which controls two flexible disk drivers 15 and 16 at the same time and a buffer 24 wherein the data read out of the copy-destination flexible disk drive by the flexible disk controller 13 are temporarily held. This disk controller 13 rotates the two flexible disk drivers 15 and 16 at the same speed simultaneously and reads the data out of the copy-source flexible disk cartridge into the buffer of the flexible disk controller 13 in byte units. Then the flexible disk controller 13 writes the data in the buffer 14 into the copy- destination flexible disk drivers 15 or 16.