A heating medium composition for suppressing deterioration of both a metal piping and a synthetic resin piping. The heating medium composition contains an antifreeze ingredient, water, a corrosion inhibitor, and a surfactant. The corrosion inhibitor includes a triazole compound, and the surfactant includes an anionic surfactant. A bag in a feeder provided in a given position along a circulation piping is filled with an oxidation inhibitor. By flowing a heating medium composition through the feeder, the oxidation inhibitor is gradually dissolved in the heating medium composition.