A background image generator 51 renders a first 3D model representing a landscape to generate a background image, an image generator 52 generates a second 3D model to be located between a camera viewpoint and the first 3D model, an image adhering unit 53 selects a specified range of the background image and adheres the background image within the selected range as a texture to the second 3D model, and a combined image generator 54 renders the second 3D model having the background image within the specified range adhered thereto and combines the rendered model with the background image to generate a combined image.