A sheet identification system comprising a sheet identification device, configured to identify a sheet under transportation, and a further identifier, the sheet identification device comprising: a standard identifier; and an option attachment member to which the further identifier is attachable, the standard identifier comprising: a standard sensor unit comprising an optical line sensor; and a standard controller comprising a first CPU and a first memory unit and configured to control the standard sensor unit and identify a type of the sheet based on an output from the standard sensor unit, the further identifier comprising: an second sensor unit configured to execute a different sensing operation from a sensing operation executed by the standard sensor unit, the second sensor unit comprising a sensor and an amplification substrate; and a second controller comprising a second memory unit configured to store a software program for the identification processing of the sheet and a second CPU configured to execute the software program, and configured to control the second sensor unit and identify the sheet based on an output from the second sensor unit,_the second controller is configured to send the results of the identification based on the data obtained from the sensor to the standard controller, the standard controller is configured to execute final identification, based on the identification results of the second controller and the identification results of itself. a standard identifier; and an option attachment member to which the further identifier is attachable, the standard identifier comprising: a standard sensor unit comprising an optical line sensor; and a standard controller comprising a first CPU and a first memory unit and configured to control the standard sensor unit and identify a type of the sheet based on an output from the standard sensor unit, the further identifier comprising: an second sensor unit configured to execute a different sensing operation from a sensing operation executed by the standard sensor unit, the second sensor unit comprising a sensor and an amplification substrate; and a second controller comprising a second memory unit configured to store a software program for the identification processing of the sheet and a second CPU configured to execute the software program, and configured to control the second sensor unit and identify the sheet based on an output from the second sensor unit,_the second controller is configured to send the results of the identification based on the data obtained from the sensor to the standard controller, the standard controller is configured to execute final identification, based on the identification results of the second controller and the identification results of itself. an second sensor unit configured to execute a different sensing operation from a sensing operation executed by the standard sensor unit, the second sensor unit comprising a sensor and an amplification substrate; and a second controller comprising a second memory unit configured to store a software program for the identification processing of the sheet and a second CPU configured to execute the software program, and configured to control the second sensor unit and identify the sheet based on an output from the second sensor unit,_the second controller is configured to send the results of the identification based on the data obtained from the sensor to the standard controller, the standard controller is configured to execute final identification, based on the identification results of the second controller and the identification results of itself.