A comment data acquisition unit acquires comment data for display over a display image, and a superimposition processing unit 162 generates a superimposition image from the comment data. The comment data includes a scaling factor or information related to the scaling factor, and a display requirement determination unit determines whether the scaling factor of the display image and either a scaling factor or information related to the scaling factor included in comment data are in a predetermined relationship. When the scaling factor of the display image and either the scaling factor or the information related to the scaling factor included in the comment data are in the predetermined relationship, a superimposition image generation unit generates a comment image using display information included in the comment data.