An image display device, an image delivery system and an image delivery server are provided by which images that are to be delivered to another digital photo frame can be easily differentiated. When an operation for replaying images is performed, the image display device starts for each image, a playback timer to measure its viewing duration and stores the viewing duration in the image file. Then, the image display device collectively transfers all the images to an image selection server at a predetermined timing or by a user operation, and the image selection server transmits images whose viewing durations are equal to or more than a predetermined threshold to another image display device as e-mail attachments at a transfer timing. As a result, the other image display device receives different interesting images every day by e-mail.