Abstract: A magnetic chemical absorbent according to the present invention is provided with a composite, which is constituted of a core substance comprising magnetite fine particles and schwertmannite being precipitated around the core substance to chemically bond therewith. This magnetic chemical absorbent can be produced in a hydrolysis reaction step, in which crystal of schwertmannite is precipitated by means of hydrolysis reaction by heating a solution of ferric salt and thereafter adding a reactive substance thereto, by means of adding magnetite fine particles into the solution after the solution is heated and before the precipitation of the crystal begins. This magnetic chemical absorbent is novel and good one whose absorption capability for harmful ion is upgraded more. In accordance with a waste-liquid treating method using this magnetic chemical substance, it is possible to intend the reduction of burdens in view of environmental and economic aspects. Moreover, this magnetic chemical absorbent is recyclable.