A resource allocation system comprising: a resource state monitoring unit which measures a capacity and/or a usage of a computer resource(s) to be managed (referred to below as “managing resource(s)”) and an allocation adjustment unit which determines a new amount of allocating resource(s) by using at least one item of information among either of capacity and usage of the managing resource, complying a resource(s) amount demanded to be allocated (referred to below as “demanded resource amount”), wherein the determined resource amount is allocated in response to a request for the resource amount.