A method of cleaning an etching chamber, with a high throughput, of a plasma processing apparatus for etching by use of hydrogen bromide (HBr) as an etching gas while holding a wafer on an electrode by electrostatic chuck. When the static charge on the wafer electrostatically chucked on the electrode is eliminated after the completion of the etching, O.sub.2 gas is introduced into the etching chamber from a gas flow-rate controller. A plasma of O.sub.2 gas is generated to cause the electric charge on the wafer to flow to the earth through the plasma, and at the same time, the interior of the etching chamber is cleaned.