A paper sheet identification system comprising a first paper sheet identification device and a second paper sheet identification device, wherein the first paper sheet identification device includes a first read unit (113,161) configured to read a specific code described on a surface of a paper sheet to uniquely specify the paper sheet, a first identification unit (111,112,114,162) configured to identify authenticity of the paper sheet using a first set value as a reference, and a first storage unit configured to store authentic paper sheets, which are paper sheets identified as authentic by the first identification unit (111,112,114,162), the first identification unit (111,112,114,162) is configured to generate previous process data in which the specific code, the first set value, and a first identification result obtained by the first identification unit (111,112,114,162) of the authentic paper sheet are associated with each other, the second paper sheet identification device includes a second read unit (313,361) configured to read the specific code described on the surface of the paper sheet, which has been taken out from the first storage unit and loaded into a slot, a second identification unit (311,312,314,362) configured to identify authenticity of the paper sheet using a second set value as a reference, a second storage unit configured to store the paper sheets identified as authentic by the second identification unit (311,312,314,362), and a first acquisition unit (350,364) configured to acquire the previous process data, and the second identification unit (311,312,314,362) is configured to perform a first process of extracting the first set value and the first identification result from the previous process data when the paper sheet is identified as a counterfeit paper sheet, which is not authentic, using the second set value as a reference, in which the first set value and the first identification result are associated with the specific code of the counterfeit paper sheet, a second process of determining whether to relax the second set value based on the extracted first set value and the first identification result, and upon relaxation of the second set value, a third process of identifying authenticity of the counterfeit paper sheet using the relaxed second set value as a reference, wherein the second identification unit (311,312,314,362) is configured not to perform the first, second and third processes if it identifies the paper sheet as an authentic paper sheet using the second set value before relaxation as a reference. the first paper sheet identification device includes a first read unit (113,161) configured to read a specific code described on a surface of a paper sheet to uniquely specify the paper sheet, a first identification unit (111,112,114,162) configured to identify authenticity of the paper sheet using a first set value as a reference, and a first storage unit configured to store authentic paper sheets, which are paper sheets identified as authentic by the first identification unit (111,112,114,162), the first identification unit (111,112,114,162) is configured to generate previous process data in which the specific code, the first set value, and a first identification result obtained by the first identification unit (111,112,114,162) of the authentic paper sheet are associated with each other, the second paper sheet identification device includes a second read unit (313,361) configured to read the specific code described on the surface of the paper sheet, which has been taken out from the first storage unit and loaded into a slot, a second identification unit (311,312,314,362) configured to identify authenticity of the paper sheet using a second set value as a reference, a second storage unit configured to store the paper sheets identified as authentic by the second identification unit (311,312,314,362), and a first acquisition unit (350,364) configured to acquire the previous process data, and the second identification unit (311,312,314,362) is configured to perform a first process of extracting the first set value and the first identification result from the previous process data when the paper sheet is identified as a counterfeit paper sheet, which is not authentic, using the second set value as a reference, in which the first set value and the first identification result are associated with the specific code of the counterfeit paper sheet, a second process of determining whether to relax the second set value based on the extracted first set value and the first identification result, and upon relaxation of the second set value, a third process of identifying authenticity of the counterfeit paper sheet using the relaxed second set value as a reference, wherein the second identification unit (311,312,314,362) is configured not to perform the first, second and third processes if it identifies the paper sheet as an authentic paper sheet using the second set value before relaxation as a reference.