A plasma processing apparatus can apply a high-quality process to an object to be processed by removing impurities from a gas-introducing part of a process chamber. The gas-introducing part connected to the process chamber so as to introduce a reactant gas into the process chamber. A first vacuum pump is connected to the process chamber so as to evacuate gas from the process chamber so that the process chamber is maintained at a negative pressure. A gas-evacuating arrangement is connected to the gas-introducing part so as to exclusively evacuate the reactant gas from the gas-introducing part. The gas-evacuating arrangement includes a second vacuum pump directly connected to the gas introducing part or a bypass passage connecting the gas-introducing par to the first vacuum pump by bypassing the process chamber.