To realize low power consumption or high speed under a read/write mode by making a revolving speed of a recording unit plate variable and making a recording frequency variable at the same rate as well.

Nw, Mw and Nm, Mm for a zone Zx belonging to a target cylinder on the recording unit plate 11 as registered in a table 181 or 182 corresponding to the zone Zx are selected in response to whether they are a high speed operation mode or a low power consumption mode, and the Nw, Mw are set in a clock generating circuit 141 while Nm, Mm a clock generating circuit 161 respectively by a controller 18. A frequency of a basic clock fm0 is multiplied by Nm/Mm by the clock generating circuit 161 to generate a clock fm to be supplied for the purpose of controlling a spindle motor 13 by a motor control circuit 16. On the other hand, a frequency of a basic clock fw0 is multiplied by Nw/Mw by the clock generating circuit 141 to generate a clock fw to be used for write operation on the magazine recording unit plate 11 by a write/read circuit 14.