PURPOSE: To confirm the file management information of a magnetic disk irrespective of connection/unconnection to a host device by adding a circuit for recording and displaying a volume name of a magnetic disk, file name of a file recorded in the magnetic disk, the used recording capacity and the remaining recording capacity to the cartridge type magnetic disk device.

CONSTITUTION: A monitoring circuit 4 monitors initialization of a magnetic disk 3 from a host device, and an instruction of generation of a file, calculates the used recording capacity and the remaining recording capacity and sends them to a recording circuit 5. The recording circuit 5 classifies and arranges information sent from the monitoring circuit 4, and records the information in a position determined in advance of a semiconductor memory 6. Also, the recording circuit 5 receives supply of a power source by a backup battery 10, and executes holding the recording contents of the semiconductor memory 6. A display control circuit 7 selects existence of a display and the display contents on a liquid crystal indicator 9 by designation of a switch 8, and executes a display of the recording contents of the semiconductor memory 6 to the liquid crystal indicator 9. In such a way, even if this device is detached from the host device, file management information can be confirmed.