An image display system includes an image capturing unit that is to be mounted on a vehicle, and is configured to capture an image of surroundings of the vehicle, a display unit configured to display a captured image captured by the image capturing unit, an image-capturing range modification unit configured to modify an image-capturing range of the image capturing unit when the vehicle is stopped, a comparison unit configured to compare an image captured before the image-capturing range is modified by the image-capturing range modification unit with an image captured after the image-capturing range is modified by the image-capturing range modification unit, and calculate a difference value therebetween, and a determination unit configured to determine whether or not there is an abnormality in the image capturing unit based on the difference value.