1. An image processing method for combining a virtual image with a shot image to obtain a combined image and displaying the combined image, the image processing method comprising: capturing a shot image picked up by an image-pickup unit; extracting a predetermined region from the shot image with an extracting unit; generating a virtual image based on a transparency parameter based on a ratio of the size of the predetermined region to the size of the shot image; combining the virtual image with a region of the shot image excluding the predetermined region to obtain a combined image; and displaying the combined image, wherein, the transparency parameter is set to be low in a case in which the ratio of the size of the predetermined region to the size of the shot image is high, and the transparency parameter is set to be high in a case in which the ratio of the size of the predetermined region to the size of the shot image is low.