The quantitative evaluation of atmospheric corrosion resistance of stainless steels exposed to a marine environment was carried out by using a newly developed electrochemical method. This new method simulates field atmospheric conditions where most of stainless steels experience rust staining under a thin electrolyte layer. The incubation time to the breakdown of passive film under a thin electrolyte layer corresponds to the rating number of initial rust staining of the specimen exposed to the actual environment for 1 year, and depends on alloy compositions. Through the analysis of change in the rating number of the specimens exposed to the marine environment for 10 years, it was clarified that tendency of the change of rating number was directly related to exposure time, not to alloy compositions. The rating number of rust staining of stainless steels after several years can be predicted from the equation introduced through the results of both the accelerated test and the exposure test.