The relationship between change in resistivity and rainfall was studied by continuously measuring resistivities of fracture zone and stratum boundary along the measuring line of 95m long from the top to bottom of rock slope. The measurement field was located on a hill of 150-200m high at the northern part of Arima-Takatsuki tectonic line. Electrodes of 30m in maximum measuring depth were arranged at 289 points by dipole-dipole method. Resistivity was continuously measured at time intervals of 6 hours. Apparent resistivity was hardly affected by rainfall at points with less infiltration of stormwater from the ground surface, while it decreased by rainfall at points on fracture zone, stratum boundary or bleeding channel. The change rate of apparent resistivity could be approximated with the exponential function of rainfall. In such case, the apparent resistivity under most dried condition at the concerned point should be used as reference maximum apparent resistivity. The change rate of apparent resistivity due to rainfall in fracture zone reflects infiltration of stormwater, suggesting to be useful for disaster prevention of slopes. 5 refs., 6 figs.