A first safety stock quantity calculation unit 81 calculates a safety stock quantity of a commodity at a first elapse time that is a time when a unit delivery time period has elapsed from one delivery time, the unit delivery time period being a unit of a delivery interval. A second safety stock quantity calculation unit 82 calculates a safety stock quantity of the commodity at a second elapse time that is a time when a coverage time period has elapsed from the delivery time, the coverage time period being a period combining a plurality of unit delivery time periods and determined depending on the commodity, the plurality of unit delivery time periods each being the unit delivery time period. A recommended order quantity calculation unit 83 calculates a recommended order quantity of the commodity, based on the safety stock quantity of the commodity at the second elapse time. In the case where prediction is made that a stock quantity at the first elapse time is less than the safety stock quantity at the first elapse time, the second safety stock quantity calculation unit 82 calculates a safety stock quantity of the commodity at a time when the coverage time period has elapsed from the first elapse time.