To design a widegolf course relatively easily without destroying a terrain as much as possible by extracting a contour part from the contour map of a land formation lot for making data, and outputting the terrain of the lot in a three-dimensional way via the establishment of height data on the basis of each line data.

A contour map is first read into a computer using an imaging scanner at a step S1, and a contour is interpolated at a step S2. Thereafter, the contour part of the interpolated image data is extracted and recognized as line data (loop data) through a three-dimensional CG software at a step S3, and the irregular parts of the lines are smoothed at a step S4. In addition, data regarding height is inputted to loop data showing each contour at a step S5 and the gap of the contour is filled with a plurality of polyhedrons at a step S6. Also, ground elements required for the golf are additionally set for the prescribed terrain part at a step S7, and color and quality feeling are established for each element at step S8. Then, a viewing position, direction or the like is set by use of the sun as a light source at a step S9 and outputted as three-dimensional computer graphics at a step S10.