A plasma processing apparatus includes a plurality of plasma processing chambers, a process gas supply line that supplies a plasma processing gas to the plasma processing chambers, a first additive gas supply line that supplies an additive gas to the plasma processing chambers, an exhaust space shared by the plurality of plasma processing chambers, and a controller. The controller determines a first plasma processing chamber group and a second plasma processing chamber group. The first plasma processing chamber group includes one or more plasma processing chambers, each of which performs the plasma processing and the second plasma processing chamber group includes one or more plasma processing chambers, each of which does not perform the plasma processing. The controller causes the additive gas to be supplied to the one or more plasma processing chambers of the second plasma processing chamber group from the first additive gas supply line.