To suppress cost up and to quickly execute consistent plotting by discriminating sticking side plotting data or stuck side plotting data, respectively retrieving the nearest 1st coordinate point and a farthest 2nd coordinate point and plotting the plotting data including coordinates far from a viewpoint at first.

When a model sort discriminating means judges the existence of sticking side plotting data, a 1st retrieving means retrieves a 1st coordinate point 21a that is the nearest to a viewpoint 23 from the plotting data. When the model sort discriminating means judges the existence of stuck side plotting data, a 2nd retrieving means retrieves a 2nd coordinate point 22b that is the farthest from the viewpoint 23 from the plotting data. A plotting means plots plotting data 21, 22 including the coordinate point far from the view-point 23 out of the 1st and 2nd coordinate points at first, and then plots plotting data 21, 22 including the coordinate point near to the viewpoint 23. The 1st and 2nd coordinate points 21a, 22b are the coordinates of vertexes of polygon data.