Abstract: An aggregation treatment apparatus for waste water which comprises a susping section for mixing particles of metal, metallic oxide or sintered metallic oxide into feed water such as sewage and drainage, and forming a slurry; an electrically aggregating section for the slurry which is installed separately from the suspending section; and a separating section which is formed integrally with the suspending section, and separating the particles from flocks in the treated water, returning the particles into the suspending section and discharging the treated water from the upper portion. The slurry is pumped from the suspending section to the electrically aggregating section. An electric field is applied to the slurry by means of an electrode tube in the electrically aggregating section, colloidal particles in the feed water is thereby aggregated to the added particles to form flocks and the treated water is then passed to the separating section.