Provided is a method for preparing boron nitride nanotubes, the method including: injecting a boron-metal catalyst composite into a reaction chamber; injecting a nitrogen precursor into the reaction chamber; producing a decomposition product of the boron-metal catalyst composite in a gas state by irradiating the boron-metal catalyst composite with a carbon dioxide laser or a free electron laser; and forming boron nitride nanotubes by reacting the decomposition product of the boron-metal catalyst composite in the gas state with the nitrogen precursor.