PURPOSE: To prevent the illegal use of a commutation ticket by finding a illegal commu tation ticket such as the copied ones.

CONSTITUTION: The device is provided with a collection section 18 discriminating 'suspicious' when commutation ticket information read at a ticket gate coincides with the ID number of any entrance commutation ticket information and when it is not matched with the ID number of any exit commutation ticket information by comparing entrance commutation ticket information with the exit commutation ticket information stored in a storage section 15. The collection section 18 obtains the differential time between the time required to read the matched entrance commutation ticket information and the time required to read new commutation ticket information as the degree of suspicion of the corresponding commutation ticket, and it stores the degree of suspicion in the storage device in the collection section 18 as well as the commutation ticket information. The time required to read the commutation ticket information stored in the storage section 15 is sent to a central collection center. The center acquires every information from the commutation ticket inspection machine of all stations, checking whether or not the same commutation ticket is used correctly in each station and discriminating the suspicious commutation ticket.