To provide a treatment method and a treatment apparatus capable of effectively, efficiently and inexpensively removing hexavalent chromium to detoxify the harmful material, and easily carrying out the detoxication without requiring high equipment cost.

A method, an apparatus and a technology of decomposing and eliminating the harmful waste by bringing a layer formed by mixing sawdust, diatomaceous earth lee and sand into contact with the hexavalent chromium to carry out physical treatment to cause a chemical reaction of the reduction of the hexavalent chromium to trivalent chromium are developed. The hexavalent chromium is stuck on soil particles and base particles of the mixed layer to be removed.