In recent years, the developement of appropriate methods to evaluate the imminence of the slope failure of rock mass appropriately and simply is urgently reruired. In this study, a estimation system of rock slope failure in the coastal areas of the Sea of Japan in Hokkaido using QT2 (quantification theory type 2) and SOM (self-organizing maps) are proposed. SOM analysis identifies the data characteristic and selects unique points. QT2 analysis examines what kind of topological and geological factors are attributed to a slope failure. Therefore, the reliability of these stability evaluation of rock slope was improved by combining QT2 with SOM.