To provide an inexpensive authentication technology with high certainty.

An authentication code information storing part 26 stores information of an authentication code corresponding to a combination of a plurality of readable codes provided in a medium for code inputting in a prescribed order. The medium for code inputting is typically paper with a barcode printed thereon. An authenticating part 26 performs authentication on the basis of the plurality of readable codes read from the medium for code inputting and the information stored in the authentication code information storing part. Authentication is successful when the plurality of readable codes are read in the prescribed order. At least one readable code that does not constitute an authentication code is desirably provided on the medium for code inputting together with the plurality of readable codes constituting the authentication code. An authentication device is configured so as to make authentication successful when only the readable codes constituting the authentication code are read from the medium for code inputting besides in the prescribed order.