Disclosed is a method for etching the inside of a tungsten CVD reaction room, in which tungsten deposited on the inside of the reaction room by a film-forming gas when a tungsten CVD reaction is conducted is removed by plasma, and which has the steps of: exhausting a remainder of the film-forming gas in the reaction room; and then supplying a high-frequency electric power into the reaction room while keeping a predetermined degree of vacuum in the reaction room and leading a mixing gas of sulfur hexafluoride and oxygen into the reaction room to generate the plasma.