An evaluation device includes a first evaluator configured, for each record used for transmission control of data circulating in a network, to evaluate extent of variation of an amount of the data, based on a history of the amounts of the data matching a condition of the record; a second evaluator configured, for each of the records, to evaluate a size of a space represented by the record, based on the condition of the record; and a calculator configured, for each of the records, to calculate an index value representing a possibility that a predetermined or a greater amount of the data matches the condition of the record within a fixed period of time, based on an evaluation result by the first evaluator, and an evaluation result by the second evaluator. Therefore, it is possible to evaluate a possibility of a sudden occurrence of a flow whose traffic volume is large.