In this study, the initial corrosion behavior of several stainless steels were examined. The materials were SUS304, SUS316 and pure Sn plate. They were decided corrosion times up to 1000hr in the use of SUS304 and 2000hr in the use of SUS316 at 500℃, respectively. After corrosion test, they were observed the cross section of reaction layer by OM and SEM. As a result, it was found that the reaction layer was formed at the interface between stainless steel and Sn plate after an incubation time. In the incubation time, the passive film made by Cr_2O_3 suppressed the diffusion of Sn into stainless steels. The strong stability of Cr_2O_3 film by the presence of Mo made strong the corrosion resistance of SUS316 against Sn higher than SUS304.