At a first timing after mounting a semiconductor wafer W on an electrostatic chuck 38, a susceptor 12 is switched from an electrically grounded state into a floated state. From a second timing after the first timing, a second high frequency power HF for plasma generation is applied to the susceptor 12, and a processing gas is excited into plasma in a chamber 10. From a third timing after the second timing, a first high frequency power LF for ion attraction is applied to the susceptor 12, and a self-bias (−Vdc) is generated. From a fourth timing close to the third timing, a negative second DC voltage −BDC corresponding to the self-bias (−Vdc) is applied to the susceptor 12. From the fifth timing after the fourth timing, a positive first DC voltage ADC is applied to an inner electrode 42 of the electrostatic chuck 38.