An image display system comprises: a transmission device (PC) 10, for transmitting image data upon receiving a drawing command from an OS or an application; and a receiving monitor 40, for displaying, on a high-resolution panel 41, image data received via a monitor cable 39, wherein the transmission device 10 includes a drawing command analysis device 20, for detecting an area on a screen wherein the content is changed by the drawing command, and for employing the detected area to calculate an area to be transmitted, and a graphics card 12, for transmitting a packet that includes the calculated area to be transmitted, and control data provided as header data for the area to be transmitted, and wherein the receiving monitor 40 includes a packet reception device 50, for analyzing the header data in the received packet and for, based on the header data, rendering image data in an internally provided frame memory.