A sheet processing apparatus that successively processes a plurality of processing-target sheets forming a sheet group, the sheet group comprising at least one sheet set (110, 120, 130, 140), the at least one sheet set (110, 120, 130, 140) comprising a bundle of banknotes and a header card (111, 121, 131, 141) that is given first recognition information, the first recognition information indicating an attribute of the bundle of banknotes associated with the header card (111, 121, 131, 141), the sheet processing apparatus comprising: a banknote inlet unit in which the sheet group is placed, the banknote inlet unit being configured to feed the processing-target sheets one by one sequentially from the bottom of the sheet group; a transport unit configured to transport the processing-target sheets fed by the banknote inlet unit; a recognition unit that is configured to recognize the banknotes in the bundle and is disposed on or above the transport unit, the recognition unit comprising a first recognition unit for recognizing at least whether or not the processing-target sheet is the header card (111, 121, 131, 141) during transportation of the processing-target sheet and a second recognition unit for obtaining the first recognition information from the header card (111, 121, 131, 141) after the processing-target sheet is recognized as the header card (111, 121, 131, 141) by the first recognition unit; and a controller including a CPU, a memory and an interface, wherein the controller generates second recognition information alternative to the first recognition information when the first recognition unit successfully recognizes the processing-target sheet as the header card (111, 121, 131, 141) and the second recognition unit fails to obtain the first recognition information, the second recognition information being temporary identification information used instead of the first recognition information, the second recognition information is information which is associated with the processing-target sheet recognized as the header card (111, 121, 131, 141), the controller storing the second recognition information in the memory, and the controller causes the sheet processing apparatus to continue banknote processing by associating a recognition result of the bundle of banknotes with the second recognition information and storing the recognition result in the memory. a banknote inlet unit in which the sheet group is placed, the banknote inlet unit being configured to feed the processing-target sheets one by one sequentially from the bottom of the sheet group; a transport unit configured to transport the processing-target sheets fed by the banknote inlet unit; a recognition unit that is configured to recognize the banknotes in the bundle and is disposed on or above the transport unit, the recognition unit comprising a first recognition unit for recognizing at least whether or not the processing-target sheet is the header card (111, 121, 131, 141) during transportation of the processing-target sheet and a second recognition unit for obtaining the first recognition information from the header card (111, 121, 131, 141) after the processing-target sheet is recognized as the header card (111, 121, 131, 141) by the first recognition unit; and a controller including a CPU, a memory and an interface, wherein the controller generates second recognition information alternative to the first recognition information when the first recognition unit successfully recognizes the processing-target sheet as the header card (111, 121, 131, 141) and the second recognition unit fails to obtain the first recognition information, the second recognition information being temporary identification information used instead of the first recognition information, the second recognition information is information which is associated with the processing-target sheet recognized as the header card (111, 121, 131, 141), the controller storing the second recognition information in the memory, and the controller causes the sheet processing apparatus to continue banknote processing by associating a recognition result of the bundle of banknotes with the second recognition information and storing the recognition result in the memory.