A model transforming data generating portion 4 extracts parameter data corresponding to a given road area from two-dimensional map data in a two-dimensional map data storage portion 3. Subsequently, the model transforming data generating portion 4 reads out pattern data corresponding to the specified road area from a pattern model storage portion 5 and generates model transforming data. An image data generating portion 6 transforms a corresponding three-dimensional map display model by using the generated model transforming data to generate three-dimensional image data. The generated three-dimensional image data is given to and displayed in a display 7. The operator operates an input portion 2 on the basis of the contents displayed in the display 7 to correct the generated model transforming data.