This paper deals with the characteristics of groundwater at different depth in a landslide slope and the mechanism of water level fluctuation in the observation borehole with a screened section along all its length. The groundwater levels and meteorological conditions have been observed at Higashimushigame landslide area since 1986. Sampled waters from the borehole were analyzed for major ion constituents.Two types of the observation borehole with a screened section only at the desired depth and along all the length, were used to measure water level and to collect water samples. Analyzing the observed data, the results are as follows: 1)Thecharacteristics of groundwater in the investigation site are divided into three groups according to the fluctuation patterns of groundwater levels and water quality. 2)Though the groundwater level in the borehole with a screened section responds to the rainfall, water quality does not change. 3) In the borehole with the screened pipe, the groundwater level observed is a function of potential and permeability in each aquifers.