The invention provides a plasma treatment apparatus or a plasma treatment method having a high productivity while maintaining a stable treatment performance. In a plasma treatment apparatus feeding a plurality of gases fed into the treatment chamber and treating a sample arranged within the treatment chamber by a plasma formed by using the plurality of gases, the plasma treatment apparatus has a plurality of feeding gas lines in which the plurality of gases respectively pass, a plurality of gas flow rate regulators respectively arranged on the feeding gas lines and respectively regulating flow rates of the plurality of gases, and a testing gas flow path coupled to the gas line so as to be arranged outside the treatment chamber and arranging a tester testing a flow rate of a gas from a gas flow rate controller therein, and the plasma treatment apparatus tests the gas flow rate regulator on a gas line corresponding to the gas which is not used for the treatment in the plurality of gases in parallel with the treatment.