The invention discloses a bank note automatic collator. The bank note automatic collator comprises a machine frame, a conveying belt, a sealed air groove and an air exhauster. A plurality of air holes are formed in the conveying belt. The sealed air groove is arranged below the upper belt surface of the conveying belt and is simultaneously communicated with a fan and the air holes. The air exhauster is arranged above the middle part of the conveying belt and generates a suction force to bank notes above the conveying belt. According to the invention, bank note are sucked by the conveying belt with the air holes, and opposite full forces are formed on the bank note with the assistance of the miniature air exhauster, so that the bank notes are conveniently unfolded and flattened; and the flatten mode of air suction forces is adopted, so that the bank note are not liable to be damaged.