An emulsifying dispersant includes, as the main component, vesicles formed from an amphiphilic substance capable of self-assembly or an emulsifying dispersant comprising single particles of a biopolymer as the main component. The particles made from amphiphilic substances capable of self-assembly are used. The amphiphilic substances are selected from among polyoxyethylene-hydrogenated castor oil derivatives wherein the average number of added ethylene oxide molecule is 5 to 15, dialkyldimethyl-ammonium halides wherein the chain length of the alkyl or alkenyl is 8 to 22, and phospholipids or phospholipid derivatives. According to the invention a three-phase structure composed of an aqueous phase, an emulsifying dispersant phase and an oil phase is formed on the surface of an emulsion to give an emulsion (such as emulsion fuel) excellent in thermal stability and long-term stability.