The present invention relates to a contrivance for inserting watermark information into a moving image. The watermark information indicative of the ownership of the copyright of the moving image is inserted into the frames of the moving image at irregular intervals, the frames being of such a number that the watermark information is visually unperceivable in the moving image. In addition, the insertion positions of the watermark information in the frames are determined on the basis of random number values. Besides, restrictive information for the copying of the moving image is inserted together with the watermark information. When the moving image has been brought to a standstill into a static image, the watermark information can be visually perceived with ease, so that illegality such as piracy can be readily exposed. Thus, the present invention can provide a simple and inexpensive scheme for the copyright protection of the moving image.