A normal three-dimensional image is presented to a person who is wearing glasses for three-dimensional image observation, and additional information including a message, disturbance information, or the like is presented to a person who is not wearing glasses for three-dimensional image observation. An image display apparatus displays, on a display unit, an image frame sequence in which additional information image frame including additional information is added between an image frame for the left eye and an image frame for the right eye. At a display timing of the additional information image frame for the display unit, the image display apparatus outputs a control signal that sets shutters for both the left and right eyes of glasses for three-dimensional image observation worn by an observer to a closed state. With this configuration, an observer who is wearing glasses for three-dimensional image observation can observe a normal three-dimensional image, and a person who is not wearing the glasses can observe additional information such as a message prompting the person to wear the glasses.