To form characters or patterns made of points or line shapes unresolvable in a photogravure orinting, as variable information on a ribbon to improve security by making it difficult to achieve confirmation by visual observation for forgery prevention in thermal transfer printing using an ink ribbon and a thermal head.

Micro characters or the like difficult to be confirmed by visual observation are printed beforehand on an infrared absorbing ink ribbon by laser, or a black image formed using an ink ribbon not absorbing in an infrared region is made a base or concealed not to be discriminated in a visible region so as to provide further security, or an image is formed on a transfer film and then transferred onto a printed body together with an image receiving layer to form the image receiving layer on the printed image, thus preventing a falsification.