A data processing device has plural kinds of recording media and a data block management device. The data block management device classifies data blocks into plural groups and records each group on an appropriate recording medium. The data block management device has a memory unit, a group reconfiguration unit and a medium selection unit. Access trend information representing a trend of combinations of former groups and latter groups is stored in the memory unit. The group reconfiguration unit performs group reconfiguration processing by reference to the access trend information. Specifically, if a sequential access trend between two different groups is increased, they are integrated to generate a new group. If a sequential access trend within a certain group is decreased, the certain group is divided to generate a new group. The medium selection unit records the new group obtained as a result of the group reconfiguration on a corresponding recording medium.