PURPOSE: To shorten the time required for exchanging a disk cassette by transferring the cassette while correspondingly moving plural shelves and a recording and reproducing device.

CONSTITUTION: Plural disk cassettes 1 incorporating optical disks are respectively housed in plural vertical staged horizontal shelves 2 of a shelf casing 4 and the casing is arranged opposing to the recording and reproducing device 3. The casing 4 is vertically moved by a mobile mechanism 5 and by the corresponding movement with the device 3 the required cassette 1 and the device are opposed to each other and the cassette is transferred between the device 3 and the case body through a transfer mechanism 6 without using a carrier. Thus the time required for the exchange of the cassette is remarkably shortened.