Martensitic Stainless Steel has high strength and hardness in comparison with other stainless steels. But the toughness and corrosion resistance is lower. So lots of researches have been done in order to improve these properties. In the previous study the alloying element of Mo resulted in increasing the toughness at tempered condition of the steel. It has been investigated in this work how the Mo addition and tempering condition influence on the various types of corrosion behavior of 13% Cr martensitic stainless steel. Corrosion resistance was hardly changed by the tempering up to temperature of 500℃, but decreased at 600℃ due to the formation of Cr carbide on the prior austenite boundary. However, the corrosion resistance increased again at 700℃, because Cr carbides were resolved and redistributed. Both general corrosion resistance and intergranular corrosion resistance of tempered steel are significantly improved with Mo content.