In an image display system that displays the condition of a person under measurement in a visible form, the person carries a PDA (10). The PDA (10) includes a bio-sensor (11) to detect bio-information on the person and an environmental information sensor (12) to acquire information on the environment around the person. The PDA (10) sends the acquired information to an image display device (20) which is connected to the PDA (10) via a network (100). The image display device (20) includes a CPU (29) that judges the condition of the person on the basis of bio-information and environmental information, generates an image representing the condition of the person and displays the image on a display unit (23).