A substrate processing system includes a monitored data receiving unit receiving a plurality of types of monitored data; a temporary memory unit periodically storing the monitored data; a monitored data rate detection unit detecting, as a monitored data rate, a total number of times each type of monitored data changes during a first time period by more than a predetermined amount; a monitored data writing allocation unit allocating a storing frequency to each type of monitored data based on the monitored data rate and an upper limit; a monitored data writing unit writing the monitored data to the temporary memory unit during the second time period based on the storing frequency; an accumulative memory unit storing the monitored data for a plurality of periods; and an accumulative data writing unit reading the monitored data for every third time period and storing the monitored data in the accumulative memory unit.