Disclosed are a method for preparing a sintered body containing cubic boron nitride which comprise the steps ofcontacting a starting material containing boron nitride and/or a starting material containing at least one selected from the group consisting of metals of groups IVa, Va and Via of the periodic table, silicon, aluminum, iron group metals and compounds of the aforesaid metals with at least one selected from the group consisting of borazine, a borazine derivative and a compound composed of boron, nitrogen and hydrogen as will release hydrogen by a thermal decomposition under pressure to form boron nitride; andsintering the material under conditions of a predetermined pressure and temperature under which cubic boron nitride is kept stable; and a method for preparing cubic boron nitride which comprises, in addition to the above steps, recovering cubic boron nitride from the obtained sintered body by a chemical and/or physical manner.These methods are considered to be greatly valuable from the viewpoint of industrial usefulness, because of being simple, very high in efficiency and excellent in economy.