Extreme Value Theory (EVT) is devoted to the statistical behavior of the maxima or the exceedances over a high threshold. The theory was originally developed in hydrology, and has recentry been applied to risk management in the field of finance and insurance. In this paper, we discuss the applicability of EVT to traffic-data analysis. Especially, using the method of EVT, we analyze a data for link-usage rate calculated from MIB (Management Information Base), and discuss the acuracy of the analyzed results.