To prevent a device from being brought into an uncontrollable condition when a trouble is generated in downloading to damage the device and to damage equipment itself in its turn, and to allow re-downloading (recovery operation).

In this image forming device, a keyword data stored in a flash memory 305 is erased when starting rewriting of a data into the flash memory 305, and the keyword data is stored again in the flash memory 305 when finishing the rewriting of the data. In the image forming device, the propriety of drive of an engine part U100 is determined based on the presence of the keyword data in the flash memory 305, and the re-download (recovery operation) to the engine part U100 is carried out when the re-download to the engine part U100 is failed.