A technique is provided, in which impure metal is efficiently separated and removed from titanium-containing raw material such as titanium slag or ilmenite and high titanium-containing raw material is produced. The method for improving quality of titanium-containing raw material containing slag, including steps of: oxidizing the titanium-containing raw material, selectively chlorinating impurities in the titanium-containing raw material, and separating and removing the impure chlorides to obtain high titanium-containing raw material. Alternatively, in this method, the oxidizing treatment and the selective chlorinating treatment are performed simultaneously.