A first system adaptation unit of magnetic tape drive apparatus communicates with a read/write request source based on a method adapted to a file system. A second system adaptation unit communicates data with the read/write request source based on a method adapted to a designated system other than the file system. A control unit allows the first system adaptation unit to be in a ready state when a format of a magnetic tape to be read and written is adapted to the file system and allows otherwise the first system adaptation unit to be in a not-ready state. The control unit deceives the read/write request source as if the first system adaptation unit is in the ready state even when the first system adaptation unit is in the not-ready state as well as the ready state.