A new sacrificial anode method was developed in this study. This sacrificial point anode method has three main features: the anode raw material is zinc, material covering the anode is mortar containing a lithium nitrite solution, and site casting is possible using a system to inject mortar on site. This method was applied to a 36-year-old RC beam that had been exposed to marine environment conditions for more than 20 years. Cracks due to steel bar corrosion were found especially on the tension side. Moreover, corrosion (rust and loss of cross-section) of steel bars embedded in the RC beam was confirmed by a partial chipping survey. After six holes 30 mm in diameter were drilled in the RC beam, this point anode was set in a position of 50 mm from the tensile steel bar, and a special mortar was injected into the hole. After this method was applied, the condition of steel bars in the RC beam was measured with an electrochemical measurement method such as electric current, potential, 24-hour depolarization, anodic polarization curve, and polarization resistance. From corrosion current density evaluated by both anodic polarization curve and polarization resistance after exposure in dry conditions for 20 months, it was confirmed that corrosion was prevented on steel bars.