Abstract: A structure of a subject such as a card, a bank note, or a stock certificate easily faked and needing authenticity validation and a method for judging the authenticity of the subject. An authenticity validation chip having structural color developers irregularly arranged is attached to a card. An optical sensor detects the arrangement of the structural color developers to individually recognize the card or judge its authenticity. To validate the authenticity, when or after the card is taken in, the information in the authenticity validation chip provided on the card is read. Each of the structural color developers is a transparent resin flake or a transparent resin thin layer. The information is read two-dimensionally with a camera, and the authenticity of the authenticity validation chip is judged by observing the distributed state of the structural color developers. Alternatively, the information can be read linearly.