To enhance the separating and removing efficiency of heavy metal ions from a waste soln. and to reduce running cost by the reduction of the adding amt. of magnetic particles to suspended particles and the reduction of the generation amt. of sludge.

An ozone injection apparatus 12 forcibly subjecting metal ions contained in a waste soln. to oxidation treatment by the injection of ozone to form insoluble oxide particles, a flocculation treatment apparatus 13 flocculating suspended matter such as org. matter or the like or oxide particles contained in the waste soln. to form flocculated particles and a magnetic filter 14 forming a strong magnetic field space by a superconductive solenoid magnet to catch particles contained in the waste soln. are arranged to a waste soln. supply piping 11 supplying the waste soln. continuously. By this constitution, both of heavy metal components and suspended components such as org. matter are collectively or indivisually caught from the waste soln. by a magnetic filter.