In a plasma processing apparatus, when pulse-modulating the high frequency power RF1 for plasma generation and the high frequency power RF2 for ion attraction with a first pulse PS1 and a second pulse PS2 having different frequencies, respectively, an impedance sensor 96A in a matching device 40 of a plasma generation system calculates an average value (primary moving average value ma) of an load impedance on a high frequency transmission line 43 for each cycle of the second pulse PS2 having a lower frequency, and outputs a load impedance measurement value based on those average values of the load impedance. Then, a matching controller 94A controls reactances of reactance elements XH1 and XH2 within a matching circuit 88A such that the load impedance measurement value is equal or approximate to a matching point (50Ω).