The rain-induced surface failure is a phenomenon under the action of the gravity force due to the interacting between geotechnical properties of the slope and the rainwater infiltration. For predicting accurately the time and places of rain induced slope failures, to make clear the behaviors of rainfall infiltration at 1-2 m thickness of in-situ slope is still the urgent problem. Therefore, a field monitoring of rainfall infiltration is being carried out at the natural Masado slopes where a debris flow was triggered during the event of June 29, 1999. The authors have already discussed in the past papers about field monitoring system and rain water infiltration processes on depths of 0.5m to 2.0m of those slopes. In this paper, newly added monitoring system to measure the change of pressure of soil moisture and moisture content at shallow part from the surface such as 0.1m- 0.3m will be introduced. And then, soil moisture behaviors on these shallow parts will be elucidated.