In this paper, the availability of the vertical electric sounding (VES) for the detection of the basal surface of the Quaternary sedimentary rocks, is discussed. Calculations were made for an objective interpretation of apparent resistivity field data obtained through the Schlumberger array. It is found that the resistivity of the Quaternary system mainly composed of gravel is as high as that of granite and the Mesozoic_??_Palaeozoic erathem. Therefore, it is difficult to make a clear distinction between the former and the latter by VES. However, the Neogene sedimentary rocks have significantly lower resistivity than the Quaternary system. This enables to detect the surface of unconformity. The relationship between the estimated depth of the basal surface and the actual one, with a high coefficient of correlation of 0.98, is shown in Fig. 7, which suggests that detection of the basal surface of Quaternary sedimentary rocks by VES can be performed within an accuracy of about 6.5m. It is concluded that VES is a useful method for estimating the depth of the basal surface of Quaternary sedimentary rocks overlying Neogene ones.