Method of producing boron trichloride

A method of producing boron trichloride, comprising performing reaction between chlorine gas in a gas containing the chlorine gas and particulate boron carbide in a state in which the boron carbide flows in the gas containing the chlorine gas, wherein,

• in the performing the reaction, the boron carbide is dropped from an upper portion of a reaction container to a bottom portion of the reaction container, and the gas containing the chlorine gas is introduced into the reaction container to flow in an opposing direction with respect to a direction of movement of the boron carbide, and
• the reaction between the chlorine gas in the gas containing the chlorine gas and the boron carbide is continuously performed, while continuously supplying the gas containing chlorine gas and the boron carbide into the reaction container and continuously exhausting a reaction product, and while an unreacted boron carbide from the reaction container drops to a receiving container that is placed below the reaction container and that communicates with a lower end of the reaction container.