A method is provided for producing cubic boron nitride, in which a mixture containing hexagonal boron nitride and a catalyst is maintained under pressure and temperature conditions that thermodynamically favor the stable presence of cubic boron nitride, thereby forming composite lumps containing cubic boron nitride, which in turn are dissolved in an alkaline solution to recover cubic boron nitride. The method is characterized by including, prior to the dissolving step, a step of decreasing the ratio of low-pressure phase boron nitride to cubic boron nitride in the composite lumps down to 50% by mass or less.