To directly update the data in a state where a flash ROM is mounted on a printed board of a controller and without separating the flash ROM from a computer and the printed board.

In this data updating device, a fixed flash ROM 20 which stores an OS(operating system) is connected to a backup flash ROM 70 which stores a BIOS for the ROM 20 via a flash RAM socket 60. Then a chip selection line 80 is connected to the ROM 70 when a jumper 40 is changed to a jumper 90. Under such conditions, the BIOS is booted to a computer to make the computer execute a flash ROM updating program. Thus, the updated data are written into the ROM 20.