An apparatus for estimating a demand for a service offered via a network includes an external-factor storing unit that stores an event for a case in which information relating to the service appears in a predetermined information source on the network, as an external factor affecting the demand; a demand-amount calculating unit that calculates an amount of the demand for the service by determining whether the event as the external factor stored is appeared in the predetermined information source; and a resource-change instructing unit that instructs a change of a resource allocated to the service, according to the amount of the demand calculated.