Reinforced concrete structures are generally repaired when cracks or exposed rebar are detected. However, considering the shortage of maintenance personnel for infrastructure facilities, it becomes necessary to continue monitoring even after rebar exposure and predict the optimal timing for repairs. Therefore, in this study, accelerated tests using simulated rebar exposure specimens and field investigations of actual structures were conducted to evaluate the progress of corrosion after rebar exposure. As a result, it was found that localized deterioration preceded the corrosion in the exposed rebar and that the expansion of the corrosion area was limited.