A cassette library (1) is provided with a driving apparatus (13), cassette housing shelves (14, 15) and a cassette carrier (16). A library controller (2) simulates as if driving apparatuses (13) having continuous address numbers were apparently used in the host computer (3) even when physically discontinuous address numbers are allocated to the driving apparatus (13), thereby making it possible to set occupancy for a driving apparatus with an arbitrary address number. The library controller (2) has the cassette carrier (16) automatically carry, at a preset timing, a cleaning cassette from the cassette housing shelf (14, 15) to the driving apparatus (13) to clean a recording reproduction head of the driving apparatus (13) using the cleaning cassette which is then carried back to the housing section in the original cassette housing shelf (14, 15) after the cleaning work.