A method is designed for forming a visual image having a specified shape on a surface of an optical disk by using an optical writing process of irradiating a laser beam onto the surface of the optical disk to form pits. The optical disk is normally capable of recording information on the surface thereof by the optical writing process. The method is carried out by the steps of acquiring image formation information associated to a visual image to be formed, forming the visual image on the surface of the optical disk based on the acquired image formation information by using the optical writing process, and recording the image formation information together with the formed visual image on the surface of the same optical disk. The image formation information contains start address information specifying a position of the surface of the optical disk to start the optical writing process for forming the visual image, stop address information specifying another position to stop the optical writing process, and pattern information specifying a pattern of irradiating the laser beam during the optical writing process.