PURPOSE:To provide an authentication card using a mark such as a bar code with invisible ink undiscernible by naked eyes such as ultraviolet ink as an authentication code and having security at a low cost and an authentication system using the authentication card. CONSTITUTION:An ID card 8 utilized as an authentication card has a paper base material 81 and a paper print layer 8b, and a transparent bar code 82 is printed on the print layer 8b. The transparent bar code 82 is used as an authentication code. Paper is used as the base material, it can be manufactured at a low cost, and it has security because a transparent invisible mark is used. The ID card 8 is issued by an authentication code registering device 1, the code corresponding to the transparent bar code 82 is stored in a registered content memory device 2. The ID card inserted into the first terminal device 5 is read by a transparent bar code reader, and the code is authenticated by an authenticating device 4. The ID card 8 is erased by an authentication code erasing device 3 after it is utilized for a preset period.
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