A design apparatus is provided for designing a probability that a delivery server or a delivery route is selected for content delivery in response to a delivery request from a user. The design apparatus receives, as input parameter values, a parameter related to a network and an estimated amount of demand for delivery requests generated by users for content, and designs a selection probability that a cache server is selected as a delivery server for content delivery or a selection probability that a delivery route is selected, using model predictive control. The model predictive control uses an objective function for reducing the number of excessive delivery requests, each of which is a delivery request generated by a user for a content item and then rejected, and said delivery route is a combination of the delivery server and a delivery path on which the content is delivered by the delivery server.