A sewage/wastewater purification system capable of easily operating reactors, improving removal ratios of organic matter, phosphorus and nitrogen, and securing quality stability of treated water by applying a combination of a suspended growth type of process and an attached growth type of process is provided. A sewage/wastewater purification system for removing organic matter, phosphorus and nitrogen comprises: an attached growth type of anaerobic process(A) for performing acid fermentation of organic matter through two individual reactors, or a first anaerobic reactor(1) out of two anaerobic reactors formed by dividing one reactor; a suspended growth type of dephosphorization process(B) using the acid fermented organic matter; and an attached growth type of denitrification process(C) of nitrifying sewage or wastewater through an aerobic filter and return nitrified water to a second anaerobic reactor(2) again to treat the nitrified water. The suspended growth type of dephosphorization process comprises a slud
