An apparatus for automatically exchanging a number of record medium cassettes. The apparatus includes a plurality of cassette exchange units 21-24. Each cassette exchange unit has a cassette storing device 32 in which a plurality of record medium cassettes are installed, one or more recording and reproducing devices 33, a cassette transporting device 34 including a cassette hand over mechanism 35 for transporting desired record medium cassettes between the cassette storing devices and the recording and reproducing devices, and a controller 39. The controllers 39 of the cassette exchange units are controlled by a system controller 40 which is connected to a host computer 70 by means of SCSI cables or interface cables 61-69. The recording and reproducing devices 33 are connected in series with the host computer 70. The cassettes can be transported between the cassette exchange units by means of bridging mechanisms 25-27.