PURPOSE: To generate an image after aliasing is removed at the time of optional-rate enlargement or reduction.

CONSTITUTION: A geometrical processing part 2 divides a body shape viewed from a view point into a trapezoid and a triangle and describes them as to shape data 1 defined by a CAD system, etc., and then stores them in a buffer 3. An image generation part 4 takes the trapezoid and triangle out of the buffer according to image generation parameters of a display range, magnification, lighting, etc., specified through an input part 7, calculates the area of bodies included in respective pixels of an image after enlarging or reducing them at the specified rate, and adds the luminance of the bodies in proportion to the area to generate a lattice-shaped digital image 5. Consequently, the image after aliasing is removed is displayed at a display part 6.