PURPOSE: To secure the symbol display of superior visibility on a three dimensional landscape diagram including a map capable of freely changing the direction of one's eye.

CONSTITUTION: In each of a map etc., storage part 1 and a symbol storage part 2, information expressing the diagram shape and its attribute and the symbol shape and its attribute of each map element is accumulated. A three dimensional landscape diagram generation part 3 generates the three dimensional landscape diagram viewed from the direction of one's eye, which is controlled by a one's eye control part 6 based on information accumulated in the map etc. storage part 1. A symbol display conversion part 4 controls a symbol surface to be always perpendicular to the direction of one's eye based on information accumulated in the symbol storage part 2 and increases the visibility of a symbol by plotting an indication line perpendicular to an X-Y plane from the symbol at need. A three dimensional landscape diagram synthesizing display part 5 synthesizes the three dimensional landscape diagram with a symbol display and output it to a display part 7.