There is provided a system or others capable of predicting a parts shipment quantity varying in accordance with an assumed parts-purchase period (such as a charge-free warranty period of a product) (having a period length with taking a product shipping date as a starting point during which a customer is assumed to purchase parts) so that prediction accuracy can be increased more than a conventional one. In the prediction system (1) for the parts shipment quantity, a server (10) has a prediction unit (100) to which product data (D1), parts shipment data (D2), and a prediction condition (D3) containing information of the assumed parts-purchase period are inputted and which performs a process of predicting a future shipment quantity for each parts and of outputting prediction result data (D0). The prediction unit (100) performs a process of predicting the future shipment quantity for each parts in accordance with the assumed parts-purchase period.