PURPOSE: An oil/water separating device for removing oil of emulsion state floating the oil in the water is provided to efficiently remove the oil which is separated due to controlling the height of a skimmer according to the oil layer and supply the oil water separating system. CONSTITUTION: An oil/water separating device includes a reservoir(10) which discharges the foreign material while precipitating precipitate and filtering the foreign material. The form divides into the first and second chambers. An oil separating tank(100) which to the second chamber after effluent from reservoir flows into the first chamber and is exhausted through the discharge hole of an exhaust passage(105) to outside. A skimmer In which the oil separating from the effluent flowing in from the first chamber is concentrated and discharged to the outside of the oil separating tank.
