There is provided a composite memory device including a recording medium and nonvolatile recording medium and in which data is written to and read from the recording mediums on the basis of a common file system, the recording medium (10) having a first data area, the nonvolatile recording medium (11) having a second data area and an identification information table to manage the first and second data area collectively. The device further includes an information selector (14) to select positional information including predetermined identification information on the basis of the identification information table, converter (15) to convert positional information selected by the information selector (14) into position information corresponding to the first data area or into positional information corresponding to the second data area, first writing unit to write data supplied from a host device to the first data area and a second writing unit to write data supplied to the host device to the second data area.