In a technology for displaying two-dimensional images on a plurality of display planes placed at different depth positions as seen from an observer to display a three-dimensional stereoscopic image, when a display object having brightness darker than that of a background is displayed, the disclosed method including: generating first two-dimensional images that are obtained by projecting the background plane onto the plurality of display planes along a line of sight of the observer, and displaying the first two-dimensional images on the display planes respectively wherein brightness of each of the first two-dimensional images is changed independently for each display plane; and generating second two-dimensional images that are obtained by projecting the display object onto the plurality of display planes along the line of sight of the observer, and displaying the second two-dimensional images on the display planes respectively in which brightness of each of the two-dimensional images is set to be the same among the display planes. In addition, when using transmissive display plane, when a display object having brightness brighter than that of a background is displayed, transparency of the first two-dimensional images are changed independently for each display plane, and transparency of each of the two-dimensional images is set to be the same among the display planes.