To improve a small image display device of the type to be attached to glasses so that positioning thereof can be made easily during use.An image display device 100 comprises a body assembly 110 which can be fixed to a temple 210 of glasses 200, and an image display section 120 adapted to move from a standby position that is located close to the body assembly 110 to a service position just in front of lenses 220. The service position for the image display section 120 is previously determined, and the image display section 120 is automatically moved from the standby position to the service position. This allows the image display section 120 to be positioned at a proper position. The image display section 120 contains a display 125 and a free curved surface prism 126 therein. A user can view images enlarged from the images produced on the display 125 when the image display section 120 is at the service position.