PURPOSE: To allow high-level and complicated sorting and improve the identification factor without increasing the identification processing time by installing multiple data collecting devices from sheets along the conveying path of sheets and collecting and identifying data in hierarchies.

CONSTITUTION: The second-stage sorting is applied to sheets having passed a data collecting device 4 by the second data collecting device 5 based on the sort result of the collecting device 4. Identification is confirmed for sheets having passed the collecting device 5 by the third data collecting device 6 based on the sort result of the collecting device 5. Identification of sheets is thus completed. The higher-level and more complicated sorting and identification can be performed by combining the simple sorting function of data collecting devices 4, 5, 6 according to such identification method by the hierarchy structure. The required time of identification processing is not increased.