The present invention is a corrosion environment diagnosis system including: an environment measuring device that includes a temperature sensor that measures temperature in an electronic part serving as a diagnosis target or an indoor space in which an electronic device including the electronic part is installed, a humidity sensor that measures relative humidity in the indoor space or the electronic device, a corrosion sensor that measures a corrosion thickness of the diagnosis target, and a database in which indoor environment data including the temperature and the relative humidity measured by the temperature sensor and the humidity sensor and corrosion thickness data including the corrosion thickness measured by the corrosion sensor are accumulated; an outside air environment database in which outside air environment data including previous temperature and humidity of outside air is recorded; and a diagnostic processing device capable of receiving data of the outside air environment database and the environment measuring device, wherein the diagnostic processing device decides a corrosion mechanism corresponding to a relation between the corrosion thickness and the relative humidity on the basis of the indoor environment data, the corrosion thickness data, and the outside air environment data, and estimates a future corrosion thickness of the diagnosis target. Accordingly, it is possible to accurately estimate a future corrosion thickness on the basis of a mechanism of corrosion by atmospheric air including corrosive gas.