Abstract: An evaporator which is formed, in combination, of a first evaporator of a centrifugal falling-film type; and a second evaporator having a shape formed of a heating side wall portion of a downward-pointing conical configuration, a cover portion defining at least one opening, through which a liquid to be treated is charged and resulting volatile components are discharged, and a bottom portion defining at least one opening permitting discharge of an evaporation residue. A scraping agitator is built in the second evaporator. The side wall portion is externally wrapped with a pipe or the like, whereby a heating medium is caused to pass therethrough for heating the side wall portion. The evaporation residue discharge opening of the first evaporator is connected to the opening of the cover portion of the second evaporator.The above evaporator is suitable to recover a volatile component from a high-viscosity liquid containing tar-like substances. It can achieve a high recovery rate.