A file management device for a control system, has a file write unit which records data of a file into cluster areas of a recording medium, records file information into a directory area of recording medium, and records FAT chain information into FAT of recording medium; a file delete unit which stores file restoration information having the file information and FAT chain information into a memory area, sends back a restoration descriptor for identifying the file restoration information to control system, and deletes the file information and FAT chain information in recording medium; and a file restoration unit which reads data of deleted file from the recording medium based on the file restoration information and sends the data back to control system, and restores the file information and FAT chain information in the recording medium based on the file restoration information of the file selected by the control system.