An environment difference detector includes an elastic surface wave element equipped with a substrate including a surface having an annular surface acoustic wave circulating path, a surface acoustic wave exciting/receiving unit exciting a surface acoustic wave along the circular path and receiving the circulated surface acoustic wave, and a sensitive film disposed on the circular path to change an elastic nature in accordance with a change in an adjacent environment, a speed/intensity measuring unit measuring a circulating speed and intensity of the surface acoustic wave from an electric signal generated by the unit when the unit receives the circulating surface acoustic wave, and an environment evaluation unit evaluating an environment adjacent to the sensitive film from at least one of the circulating speed and the intensity measured by the unit.