To surely prevent heavy metals from eluting from a waste material containing heavy metals and to prevent the waste material containing the heavy metals from scattering by solidifying it.

The treating agent for the waste material containing the heavy metals contains alumina cement in which the molar ratio of CaO to Al2O3 is 1.0 to 2.5, a water-soluble compound of phosphoric acid and water. The method for treating the waste material containing the heavy metals comprises adding the alumina cement in which the molar ratio of CaO to Al2O3 is 1.0 to 2.5, the water-soluble compound of phosphoric acid and water to the waste material containing the heavy metals and kneading the resulting mixture.