PURPOSE: To shorten processing time and to reduce the load of a main computer by searching graphic data and fetching them from an external storage by the main computer based on the identification codes of points and lines constituting a designated graphic.

CONSTITUTION: When coordinate values for the picture of a graphic display device 12 are inputted from a coordinate input device 10, concerning these coordinate values, prescribed coordinate transformation is executed in the graphic display device 12 and the values are transferred to a main computer 16. Based on the transferred and inputted coordinate values, the main computer 14 sets the designation of the desired graphic, out of the displayed graphics, while turning ON a detection attribute related to this graphic. Based on the coordinate values, the main computer 16 executes the search of identification codes ID concerning the points and lines constituting the graphic and the ID obtained from this search is transferred to the main computer 16. Then, a hardware disk device 14 is searched and the desired graphic data are fetched.