To provide a method for simply and efficiently carrying out liquid-liquid extraction for much quantity of the liquid flow, adaptable to a wide range of operating conditions, and particularly useful for the extraction of valuable components from the waste water over 50 t/hr from an apparatus for producing high-purity terephthalic acid. The liquid-liquid extraction method is characterized in that the waste water is mixed with an extract agent for extracting an objective component from the waste water in the piping structured for their mixture, and that the mixture is subsequently supplied into avessel with its flowing speed decreasing caused by gravity in order to settle the mixture in it for the liquid-liquid extraction.