An image display device includes an excitation light source; a fluorescent screen including a plurality of phosphor regions that are repeatedly formed in an in-plane direction and a retro-reflection region that reflects a part of incident light in the opposite direction of the incident light; a scanning unit that scans a surface of fluorescent screen on which the phosphor regions and the retro-reflection region are formed with excitation light from the excitation light source; a photo detection unit that outputs signal value that varies on the basis of an incident light amount onto the photo detection unit; a reflection unit that reflects retro-reflection light of the excitation light directed from the retro-reflection region to the photo detection unit; and a control unit that causes the scanning unit to scan the fluorescent screen, detects boundaries between the phosphor regions and the retro-reflection region on the fluorescent screen.