A wastewater purifying apparatus has plural treatment chambers for stepwise purifying wastewater discharged from a lavatory, a storage chamber for storing purified wastewater derived from the downstream-most treatment chamber, and a purified wastewater storage tank. A suction port is formed in the upstream-most treatment chamber for sucking the wastewater. Refluxing equipment refluxes wastewater from the treatment chambers downstream of the upstream-most treatment chamber into the upstream most treatment chamber. A purified wastewater supplier supplies the purified wastewater in the purified wastewater storage tank into the upstream-most treatment chamber. The above arrangement performs expedient and sophisticated purification treatment of the wastewater containing sludge components, such as sewage discharged from the lavatory, or miscellaneous effluents generated by pulverizing garbage by a disposer. The arrangement also simplifies washing of the apparatus.