To provide a wastewater treatment method which can efficiently remove offensive odors in the treated water of sewage wastewater, industrial wastewater and the like to contribute environmental conservation.

Treatment tanks for performing the wastewater treatment of raw wastewater containing organic matter, nitrogen, sulfur, etc. discharged from a lens factory are arranged in the order of a raw wastewater tank 1, a first pH adjustment tank 2, a biological treatment column 3, a second pH adjustment tank 4, a coagulating sedimentation tank 5, an ozone dissolving tank 6, an activated carbon column 7, and a third pH adjustment tank 8. In the ozone dissolving tank 6, ozone is dissolved in treated water to perform oxygen dissolution treatment for increasing dissolved oxygen concentration in the treated water. The treated water is flowed into the activated carbon column 7 to perform activated carbon treatment for adsorbing organic matter contained in the water on activated carbon to remove it. Oxygen gas obtained by decomposing ozone not dissolved in the treated water during the oxygen dissolution treatment process by an ozone decomposition catalyst is supplied into the activated carbon column 7.