New amphoteric surfactants which possess an acceleration effect and give a stable emulsion were prepared for metal extraction by liquid surfactant membranes (henceforth LSM). Copper extraction by LSM using the amphoteric surfactants was carried out in a stirred tank and the W/O emulsion was demulsified by a continuous electrical coalescer. The amphoteric surfactants formed a stable emulsion at low concentration which is about one-tenth the corresponding concentration of Span 80 or Polyamine. By using the amphoteric surfactants, the extraction rate was increased about ten times as compared with the nonionic and cationic surfactants. The acceleration effect is considered to be caused by an electrostatic interaction between copper ion and hydrophilic phosphoric-group of the amphoteric surfactants. The increase of the extraction rate leads to shortening the operation time in the LSM process. Furthermore, the emulsion made of the amphoteric surfactant could be efficiently demulsified by an electrical coalescer.