Mercury movement in incineration treatment of organic liquid waste at university was investigated. This experiment was carried out using organic liquid waste discharged from the laboratory into which definite mercury was added and the spray-incineration treatment facility at Okayama university. From mass balance most of mercury in flue gas was not trapped by the gas washer. This result showed the vapor-phase mercury treatment was indispensable to the flue gas treatment process.<BR>Lead-mercury substitution method was effective for vapor-phase mercury. And we estanblished the mercury removal process consisted of the 90cm diameter mercury treatment tower. Pumice upon which PbS was deposited were packed in this tower.<BR>Pressure drop in this process was smaller than in conventional activated carbon adsorption method. And the removal ratio of mercury for the flue gas in which the range of mercury concentration was 0.03-5mg/Nm³, were more than 90%. By this process, mercury concentration in flue gas from this treatment facility could keep below the standard value for working environment, 0.05mg/Nm³.