A sheet processing machine transmits information indicating a degree of contamination or damage for each sheet detected by a discrimination unit to a teller PC as a discrimination result. The teller PC saves the discrimination result received from the sheet processing machine in a data storage unit. A CPU of the teller PC decides reference levels that can attain good bill ratio designated by the user for respective items required to discriminate good/bad states of a sheet based on the previous discrimination results saved in the data storage unit. The CPU of the teller PC sets the reference levels that can attain the good bill ratio designated by the user in the discrimination unit of the sheet processing machine. The discrimination unit set with such reference levels discriminates good/bad states of sheets based on the reference levels set by the teller PC.