PURPOSE: To make it possible to quickly recognize the image of a field by overlapping the symbol of alarm contents to storage contents storing a photographed image and displaying the overlapped contents.

CONSTITUTION: A photographed image retrieving means 4 allocates a corresponding photographed image screen 8a from a photographed image file 1 based upon an alarm inputted from an alarm input means 3 and an alarm symbol 8c is picked up by a symbol retrieving means 5. Then a character information forming means 6 forms character data 8b and these three information are displayed on the same CRT screen 8 by an overlapped screen display means 7. Consequently, a real place can be recognized.