To provide an information storage device in which data of a second kind can be protected from a write-in output while performing usually the write-in output of data of a first kind by an external computer.

The device is provided with: a first storage region in which data of the first kind are stored in the information storage device; a recording medium having a second storage region in which data of the second kind used for reading and writing data of the first kind is stored; an access part in which when a second system command is received, the write-in and/or output of data of the second kind is performed by accessing to the second storage region, when a first system command is received, the write-in and/or output of data of the first kind is performed by accessing to the first storage region using data of the second kind, and an obstruction part for obstructing that the access part accesses to the recording medium conforming to the second system command when suggestion information suggests that data of the second kind are in a state to be protected.