An image combining method for combining an image obtained by image sensing real space with a computer-generated image and displaying the combined image. Mask area color information is determined based on a first real image including an object as the subject of mask area and a second real image not including the object, and the color information is registered. The mask area is extracted from the real image by using the registered mask area color information, and the real image and the computer-generated image are combined by using the mask area.