Links are set among three hierarchical data and one moving image data. When a display area overlaps with a first link area while an image is being displayed by using first hierarchical data, switching to display by use of the 0-th hierarchical level of the second hierarchical data is made. When the display area overlaps with a second link area while an image is being displayed by using the second hierarchical data, switching to display by use of the 0-th hierarchical level of the third hierarchical data is made. The link destination of another link area is the moving image data and moving image reproduction is started as a result of zoom-up of this area. The hierarchical data are held on the client terminal side and the data existing on the other side of a switching boundary are transmitted to the client terminal in a data stream format.