A recording tape cartridge is structured so as to accommodate, within a case, a reel on which is wound a magnetic tape which is a recording medium. The recording tape cartridge has a so-called WORM function such that overwriting of data on a recording region of the magnetic tape where data is already written, is prohibited. Within the case are provided a first memory board which stores data managing information for managing data written on the magnetic tape, and a second memory board which stores WORM managing information for managing writing of data to the magnetic tape.