For the long-term integrity of concrete cask in the delivery and storage system of spent fuel, the relationship between chloride ion permeability of concrete and corrosion rate of reinforcing steel by chloride ion is discussed. Chloride ion permeability based on charge passed and penetration depth of chloride ion, corrosion rate of reinforcing steel by chloride ion are measured for 24 types of concrete which are made by experimental parameters such as water-binder ratio, the type and replacement ratio of admixture materials etc. As a results, the resistance of concrete to the penetration of aggressive media is classified by the chloride ion permeability based on the charge passed. There is a good relationship between chloride ion permeability of concrete and corrosion rate of reinforcing steel by chloride ion. Thus, the chloride ion permeability based on charge passed may be used as the technical data for durability design of RC structures to the penetration of aggressive media.