An image generating apparatus generates a computer graphics image by rendering a polygon, and includes a coordinate data loading unit which loads coordinate data in vertex data of a vertex of the polygon, a coordinate transformation unit which transforms a coordinate of the loaded coordinate data into a coordinate in a different coordinate system, and a polygon removal determining unit which determines whether the polygon is to be rendered or not, using transformed coordinate data obtained through the transformation. A vertex removal determining unit determines the vertex to be valid, a form data loading unit loads the form data corresponding to only the vertex that is determined to be valid, and a polygon rendering unit renders the polygon using the loaded form data and the transformed coordinate data.