To provide a treatment apparatus for solid containing harmful substances such as organic halogen compounds with reduced running cost.

A treatment method for solid containing harmful substances such as organic halogen compounds is provided for decomposing the harmful substances by introducing the solid containing harmful substances such as organic halogen compounds into a casing 30 and irradiating them with microwaves, wherein remaining heat of the solid after irradiation of microwaves is used as a heat source for the solid introduced into the casing 30.