A method of calcining an electrode material using a rotary kiln comprising a heat treatment section which has a cylindrical kiln shell, a supply section for introducing a process material into the kiln shell, and a discharge section for discharging the process material from the kiln shell, wherein the method comprises: introducing particles of the electrode material into the upper part of the kiln shell; flowing a positive pressure gas through the inside of the kiln shell and calcining the electrode material particles while moving them from the upper part to the lower part of the kiln shell; and discharging the electrode material particles from the lower part of the kiln shell.