An evaluation pair extraction unit analyzes a document which is present on a network to extract an evaluation pair composed of an object and an evaluation expression, and registers it in an evaluation pair database. An evaluation pair analysis unit executes analysis such as category estimation, specific evaluation expression extraction, and comparative analysis by utilizing the evaluation pair of the database. The evaluation pair is data in which the object and the evaluation expression are combined; wherein the object is a unique object including a commercial product name, maker name, or the like which can be evaluated, and the evaluation expression of the evaluation pair is a phrase representing evaluation including like, hard to use, or the like. An evaluation pair extraction unit gives an evaluation pair extracted from a model document to a machine leaner to cause it to learn a rule which can serve as an evaluation pair, and, after the learning, correctly combines an object with an evaluation expression from an unknown document to extract an evaluation pair.