PROBLEM TO BE SOLVED: To provide a method for concentrating a platinum group element, rhenium and arsenic in a substance to be treated which contains the platinum group element, rhenium and arsenic respectively, and separating each element from the others. SOLUTION: This separating method includes: leaching the substance to be treated such as dust, which has been collected from an exhaust gas produced when various catalysts or the like, for instance, have been melted and smelted in an electric furnace and an oxidation furnace, and contains the platinum group element, rhenium and arsenic, with an alkaline solution such as an NaOH solution; subsequently separating a solid in which the platinum group element is concentrated, from a solution in which the rhenium and arsenic are leached; then adding a chloride such as potassium chloride into the solution; and subsequently separating the solid in which the rhenium is concentrated, from a solution in which the arsenic is concentrated. A liquid temperature in the step of adding the chloride and the subsequent step of solid-liquid separation is preferably 20-40°C. COPYRIGHT: (C)2010,JPO&INPIT