PURPOSE: To accurately plot the wide line graphic having such crossing part as typically represented by crossroads on solid crossing points on maps by a simple operation.

CONSTITUTION: A crossing point retrieval part 72 retrieving the crossing point part to cross the road graphic on a crossing point data buffer part 52 or a road data buffer part 51 when the road data showing the road graphic is prepared, a crossing point data preparation part 73 preparing the crossing data showing the crossing form of the retrieved crossing point part and writing the data in the buffer part 52 and a data for display preparation control part 81 are provided. The data for display preparation control part 81 prepares the linear graphic data for display that unnecessary part on the image edition is eliminated from the linear graphic composing the road graphic from the crossing form based on the content of the buffer parts 52, 51. At this point, the crossing point data showing the crossing form is successively switched and changed every time the switch is designated from a keyboard 1.