Method of producing boron trichloride

A method of producing boron trichloride, including:

• a metal chlorination step of bringing a gas containing chlorine gas into contact with raw boron carbide as boron carbide comprising, as an impurity, a metal other than boron, at a temperature of 300° C. or more and 700° C. or less, and allowing the metal to react with the chlorine gas in the gas containing the chlorine gas, to form a metal chloride and to obtain boron carbide containing the metal chloride;
• a removal step of removing the metal chloride from the boron carbide containing the metal chloride, obtained in the metal chlorination step;
• and
• a generation step of bringing a gas containing chlorine gas into contact with the boron carbide from which the metal chloride has been removed in the removal step, and allowing the boron carbide and the chlorine gas in the gas containing the chlorine gas to react with each other to generate boron trichloride wherein the boron carbide and the gas containing the chlorine gas are brought into contact with each other at a temperature of 550° C. or more and 1100° C. or less in the generation step.