The invention relates to a method for the purification of gasification gas obtained from a carbonaceous material. The purification is carried out by adding oxygen or an oxygen-containing gas to the gasification gas and by contacting the gas mixture with a solid catalyst. According to the invention the catalyst contains at least one zirconium compound, such as zirconium oxide, which is used in particulate form as such or, for example, combined with an inert, honeycomb-structured support. By the purification, ammonia and organic tarry impurities can be removed from the gas simultaneously.