With a conventional image-display system, a presenter sometimes has difficulty in providing every viewer with an easy-to-see picture. When projecting an image transmitted from a computer operated by the presenter and enabling the viewer to watch the image projected by the projector, the projector receives image data transmitted through two-way communication from the computer operated by the presenter, projects an image represented by the received image data and transmits the received image data to a client computer operated by the viewer through the two-way communication, and the client computer receives the image data transmitted through the two-way communication and displays the image represented by the received image data on its display.