Abstract: The present invention discloses a process for breaking an emulsion comprising water and oil, comprising the steps of mixing an emulsion consisting of water and oil with a culture, bacterial cells or a culture supernatant of a bacterium belonging to the genus Alteromonas or the genus Rhodococcus capable of breaking an emulsion comprising water and oil; and consequently separating said emulsion into an aqueous layer and oil layer; and, a process for breaking an emulsion comprising water and oil, comprising the steps of mixing an emulsion comprising water and oil with bacterial cells of a bacterium belonging to the genus Aeromonas capable of breaking an emulsion comprising water and oil so as to form an aqueous layer and an aggregated layer consisting of bacterial cells and oil, and then separating these layers.