The invention relates to a bank note processing machine and a method for recognizing forged bank notes.With the bank note processing machine according to the invention and the method for recognizing forged bank notes according to the invention the starting point is that the bank notes to be checked are compared with comparative data that are derived from authentic bank notes and known forgeries, additional comparative data of new types of forgeries being used and the bank notes to be checked being compared with both the comparative data and the additional comparative data for new types of forgeries, so as to determine whether a forged bank note is present.