An electronic watermarking embedding-processing section acquires layout information which specifies an embedding area of first sub information and an embedding area of second sub information in main image information. The electronic watermarking embedding-processing section performs overlapping processing for invisibly embedding the first sub information in the embedding area of the first sub information in the main image information which is specified by the layout information. The electronic watermarking embedding-processing section performs overlapping processing for invisibly embedding the second sub information in the embedding area of the second sub information in the main image information which is specified by the layout information. The electronic watermarking embedding-processing section creates composite image information by composing image information in which the first sub information is invisibly embedded in the main image information and image information in which the second sub information is invisibly embedded in the main image information.