1. An image display method for displaying an image while shifting it, comprising: a process of reading in image data; a process of reading in a shifting parameter specifying how the image is shifted; a shifting parameter/image data adjustment process of reducing a viewpoint shifting deviation, which is a difference between an optical flow determined between display images of frames that are adjacent in time and the actual movement of pixels of the image, based on the read-in image data and shifting parameter, and adjusting at least one of the shifting parameter and the image data such that a shifting amount of the image between frames that are adjacent in time is increased; a display image creation process of creating display images by processing the read-in image data and background image data in accordance with the adjusted shifting parameter or image data; and a process of displaying the created display images on a display device.