1. An image display device worn on a head or face, comprising: a display configured to be disposed at an eye position of a user wearing the image display device on his or her head or face; a processing device configured to control: acquiring an image of a real world; specifying a region in which to display the image of the real world; mixing the image of the real world into a virtual image on a basis of the region specified; and generating an image to display on the display by mixing the image of the real world, in which the image of the real world corresponds to the region specified, into the virtual image, wherein the image of the real world is positioned in an area of the virtual image corresponding to the region specified.