Ni-Ti alloy have been investigated for applying in various surgical procedures in these days. However, little is known about the toxicity of Ni-elements and the actual conditions of surface modification of Ni-Ti alloy. In this study, the corrosion resistance of Ni-Ti alloy was improved through making TiO_2 thin film by in air oxidation and reactive sputtering. These thin films were characterized using FE-SEM, XRD, XPS and Electrolysis Reduction. And judging from the polarization curves obtained by electro-chemical measurement in quasi-living body environment, corrosion resistance of Ni-Ti super elastic alloy was evaluated. From these considerations, some trials were conducted for establishing a method for TiO_2 thin film formation method on the surface of Ni-Ti alloy.