To provide an apparatus for detoxifying a heavy metal-containing composition which can attain simplification and miniaturization of the apparatus while enhancing reaction efficiency and can attain reduction of energy cost too.

The apparatus 1 for detoxifying the heavy metal-containing composition is provided with a negative pressure producing means which produces negative pressure by jetting an acid or an alkali solution as a high-pressure fluid into a reaction pipe 10, a warming means which warms a mixture obtained by mixing high-pressure fluid with the heavy-metal-containing composition sucked in from a storage tank 13 into the reaction pipe 10 by the negative pressure produced by the negative pressure producing means and an electromagnetic wave irradiation means which irradiates the warmed mixture with electromagnetic waves. The warming means and the electromagnetic wave irradiation means are successively disposed in the reaction pipe 10 on a downstream side of the negative pressure producing means.