Suzhou Nutpool Materials Technology Co., Ltd

A spherical boron nitride fine particle suited for use as a highly thermoconductive filler or the like has an average particle diameter of 0.01 to 1.0 μm, an orientation index of 1 to 15, a boron nitride purity of 98.0% by mass or greater, and an average circularity of 0.80 or greater. A method of producing a spherical boron nitride fine particle includes reacting ammonia with an alkoxide borate at an ammonia/alkoxide borate molar ratio of 1 to 10 in an inert gas stream at 750° C. or higher within 30 seconds, then applying heat treatment to a reaction product in an atmosphere of ammonia gas or a mixed gas of ammonia gas and an inert gas at 1,000 to 1,600° C. for at least 1 hour, and further firing the reaction product in an inert gas atmosphere at 1,800 to 2,200° C. for at least 0.5 hour.