This paper examines the applicability of electrical resistivity prospecting to landslide investigations based on the effect of the physical properties of rock on resistivity. Resistivity data measured in the laboratory shows that the resistivity of rock depends mostly on its porosity, water saturation, pore fluid resistivity, and intrinsic matrix resistivity with weathering and alteration. In the case of water-saturated rock, resistivity is mainly affected by porosity, pore fluid resistivity, and intrinsic matrix resistivity, but the resistivity of unsaturated rock is mostly affected by the degree of water saturation. Based on these results, the distribution of slip surfaces, geological structure, and regions of landslide was estimated by combining existing borehole logs and underground observation data with resistivity distribution in a Tertiary landslide area. Therefore, it was confirmed that the application of electrical resistivity prospecting to landslide investigations is an effective research method.