PROBLEM TO BE SOLVED: To provide a liquid processing method and a liquid processing apparatus for stably processing a liquid to be processed regardless of the electric conductivity of the liquid to be processed. SOLUTION: A first processing electrode 12 is arranged on one end side and a second electrode 31 is arranged on the other end side. Is introduced to swirl the liquid L1 to generate a gas phase G in the swirling flow F1 of the liquid L1. By applying a voltage between the first electrode 30 and the second electrode 31, Then, plasma P is generated to process the liquid L1. The electrical conductivity of the liquid L1 is measured, and the liquid supply unit is set based on the correlation between the flow rate of the liquid to be treated introduced into the treatment tank and the electrical conductivity with respect to a predetermined hydrogen peroxide production amount per unit time. It is controlled by the control unit 73 to increase or decrease the flow rate of the liquid to be treated introduced into the treatment tank. [Selection diagram] Figure 1【課題】被処理液体の電気伝導度によらず、安定して被処理液体を処理する液体処理方法及び液体処理装置を提供する。【解決手段】一端側に第１電極３０が配置され、他端側に第２電極３１が配置された断面形状が円形である筒状の処理槽１２に、処理槽１２の接線方向から液体Ｌ１を導入することにより液体Ｌ１を旋回させて、液体Ｌ１の旋回流Ｆ１中に気相Ｇを発生させ、第１電極３０と第２電極３１との間に電圧を印加することにより気相Ｇ中にプラズマＰを発生させて液体Ｌ１を処理する。液体Ｌ１の電気伝導度を測定し、単位時間当たりの所定の過酸化水素生成量に対する、処理槽に導入する被処理液体の流量と電気伝導度との相関関係とに基づいて、液体供給部を制御部７３で制御して、処理槽に導入する被処理液体の流量を増減させる。【選択図】図１
