PURPOSE: To shorten the processing time required for reading and writing data from and to a medium.

CONSTITUTION: The integrated data 16 from a host device 7 are divided into the number of heads 11 to 14 stored in a ROM 5 by a data transforming circuit 6. Each of heads is moved to the top of media 81 and 82 by a head control circuit 4 and a head driving circuit 3 and writes the data. Moreover, divided data 151 to 154 are read by each head from the media 81 to 82, integrated with the integrated data 16 and transmitted to the host device 7.