To effectively download software by updating software version management and software.

A common monitoring CPU unit 200 has an electrically erasable and writable nonvolatile storage element 3 where the same software is inputted from outside and stored, CPU units 301-30n for individual control store software for a communication and file transfer with the common monitoring CPU unit 200 and deciding normalcy and stores software transferred from the erasable and writable nonvolatile storage element 3, and the CPU units 301-30n for individual control decide the normalcy of the transferred software and informs the common monitoring CPU unit 200 of the result; and the common monitoring CPU unit 200 when receiving normalcy decision information indicates the execution of the software to the CPU units 301-30n for individual control, but when abnormality decision information is received, the software is retransferred from the erasable and writable nonvolatile storage element 3.