An information processing apparatus has a disk shuttle to mount a magnetic disk unit, a main body case to contain at least one disk shuttle, a connector of magnetic disk provided at the insertion end of the disk shuttle inserted from one side of the main body case, a connector of a main body provided in the other side of the main body case and fitted with the connector of the magnetic disk, a back plane to be fixed with the connector of the main body, an tenon formed at the insertion end of the disk shuttle and extending toward the back plane, and a mortise formed in the back plane to be fitted with the tenon, thereby locking the movement in the direction transverse to the inserting direction of disk shuttle.