PURPOSE: To enable the mounting of various kinds of disk enclosures of small sizes and large capacities by mounting the disk enclosures via an adapter to a case and using the adapter meeting the disk enclosures.

CONSTITUTION: The bottom of the adapter 22 is projectingly provided with guide projections 22a corresponding to mounting holes 30a, 31a of the disk enclosures 30, 31. The front end thereof is provided with holes 22b facing the holes 30a, 31a and the enclosures 30, 31 are mounted to the adapter 22 by screwing thereto. Further, a junction base plate 32 is mounted by using the mounting projections 33c formed on the side wall of the adapter 22. As a result, the enclosures are mounted via the adapter 22 to the case 21 and since the shape thereof is not restricted, the grade up of the device is easily executed on site.