Masado, sandy soil of heavily weathered granite, is widely dispersed in Chugoku region. Heavy rainfall had repeatedly caused slope failures and debris-flows that had led to severe damages to both life and property in this region. To mitigate this kind of disaster is essential for this district because the urbanized area is expanding towards the foothill of the slope due to lack of housing space. To develop a better model to predict a rainfall induced slope failures, study on a past case occurred on the Hiroshima University premises, geophysical investigation on this slope nearby the failed section, and a series of model tests on slope failure caused by artificial rainfall were conducted. Sensors to monitor the moisture change in the surface layer of the slope were installed on this failed slope at field. This paper presents the results of the study on the surface layer of the Masado slope on the University premises together with the field monitoring system.