The invention discloses a separation device of volatile organic compounds in sewage, and belongs to the technical field of water treatment. The device comprises a sewage treatment tank and a condenser, wherein the sewage treatment tank is divided into a water vapor generation cavity and a steam mixing cavity by virtue of a conduction isolation area; a heater is arranged at the bottom of the water vapor generation cavity; the upper part of one side of the steam mixing cavity is communicated with the condenser; the water vapor generation cavity is positioned below the steam mixing cavity, and is communicated with the steam mixing cavity by virtue of a water vapor channel. The technical scheme of the separation device indirectly performs heating on liquid to be treated by using high-temperature steam, combines the process of evaporating water into steam with the separation process of the volatile organic compounds, simplifies the structure of the device, reduces the heat loss and substance loss in the water treatment process, drives the volatile organic compounds to realize temperature-controllable volatilization by using high-temperature water vapor, forms saturated water vapor above the liquid to be treated, inhibits the evaporation of water in the liquid to be treated, and can be used for effectively ensuring the concentration of treated liquid after the volatile organic compounds are separated.