Abstract: A process comprises forming ruthenium tetroxide by blowing ozone-containing gas into crude ruthenium powder while hypochlorous acid is being added to the powder, allowing a hydrochloric acid solution to absorb the ruthenium tetroxide, evaporating the solution to dryness, and roasting the RuOCl.sub.3 crystals thus obtained in a hydrogen atmosphere. Thus a high-purity ruthenium material for thin film deposition, typically sputtering targey, is obtained which contains less than 1 ppm each of alkali metal elements, less than 1 ppm each of alkaline earth metal elements, less than 1 ppm each of transition metal elements, less than 10 ppb each of radioactive elements, a total of less than 500 ppm of carbon and gaseous ingredient elements, the material having a purity of ruthenium of at least 99.995% excluding the gaseous ingredient elements.