Cathodic protection methods have been given attention as one of the effective countermeasures against salt induced damage of reinforced concrete (RC) members. In this paper, a series of experiments was executed in order to examine the effects of chloride content gradient of concrete from the surface to the inside of concrete and multi-layered arrangement of reinforcing steel bars on the effects of cathodic protection. 　The following results were obtained. (1)Macro-cell corrosion current flowed out of the steel bars in outer layer of concrete having high amount of chloride ions to those in inner part of concrete having less amount of chloride ions. (2)When all steel bars were short-circuited protective current from the anode attached on the surface of concrete flowed mainly into the steel bars in outer layer of concrete. (3)In case of relatively high chloride ion content in concrete, macro-cell current was large and protective current density of 2-4mA/m2 was needed to eliminate those macro-cells. (4)In case of relatively high chloride ion content in concrete, protective current density of 20-40 mA/m2 was needed in order to polarize the steel bars inside of concretes as much as 100mV, which was 2-5times larger than for the bars in outer layer of concrete. (5)In case of small amount of chloride ion in concrete, protective current density less than 1mA/m2 was enough to polarize all the bars in concrete up to 100mV.