A condition information acquisition section of an image generation device acquires a condition of communication and condition information of a head-mounted display. An image generation section generates a display image including distorted images for a left eye and a right eye. A reduction processing section converts the display image to data in which different regions have different reduction ratios in accordance with the condition of communication, etc., and transmits the data through an output section. An image size restoration section of the head-mounted display restores the transmitted data to the display image in an original size to cause the display image to be displayed by a display section.