1. A method of evaluating a value of reference information, the method comprising: a first step of receiving a request to evaluate a value of reference information of a first reference document among reference documents of a subject document; a second step of calculating similarity values of reference relationships between the subject document and each of neighbor documents, respectively, and summing the calculated similarity values to calculate a first sum, the neighbor documents referencing the first reference document; a third step of multiplying each of the similarity values of reference relationships between the subject document and each of the neighbor documents by a corresponding value of reference information of the first reference document for each of the neighbor documents, and summing the multiplied values to calculate a second sum; a fourth step of updating an initial value of a value of the reference information of the first reference document for the subject document by using a ratio of the second sum to the first sum to; and a fifth step of applying the second to fourth steps to the reference documents, to update values of the reference information for each of the reference documents.