This grain management system is provided with a combine and a management server 8. The combine is provided with: a grain measurement unit 30 which outputs measurement values related to the composition of harvested grain supplied to a grain tank 16； and a data transmission unit 51a which transmits to the management server 8 via a communication line the measurement values and field identification information for specifying a field. The management server 8 is provided with: a reception unit 81b for receiving from the combine the measurement values and the field identification information； a table management unit 83 which on the basis of the field identification information determines a measurement value/grain composition value table for deriving grain composition values from the measurement values； and a grain composition value calculation unit 82 which uses the measurement value/grain composition value table determined by the table management unit 83 to obtain the grain composition values from the measurement values.
