A method for controlling a driving frequency of a pulsed variable frequency RF generator to perform impedance matching between the pulsed variable frequency RF generator and a load, the pulsed variable frequency RF generator providing RF power to the load as a pulse of an ON-time period T_ON and an OFF-time period T_OFF, which alternate, and including a control loop varying a driving frequency in the ON-time period T_ON, the control method comprising: varying a driving frequency f(n,m) in an ON-time period T_ON(n) of an n-th pulse comprising: a first step of measuring an RF current signal I and an RF voltage signal V at an output terminal of the pulsed variable frequency RF generator in the ON-time period T_ON(n) of the n-th pulse; a second step of calculating an impedance Zi and a reflection coefficient Γi at the output terminal of the pulsed variable frequency RF generator by using the RF current signal I and the RF voltage signal V in the ON-time period T_ON(n) of the n-th pulse, calculating a phase-shifted reflection coefficient Γ' from the reflection coefficient Γi to reflect a phase shift caused by a transmission line coupled between the load and the pulsed variable frequency RF generator, and calculating a phase-shifted admittance y' converted from the phase-shifted reflection coefficient Γ'; and a third step of selecting an increasing or decreasing direction of the driving frequency of the pulsed variable frequency RF generator depending on a sign of an imaginary part Im(Γ') of the phase-shifted reflection coefficient in the ON-time period T_ON(n) of the n-th pulse and varying the driving frequency, and repeating the first step, the second step, and the third step until the ON-time period T_ON(n) of the n-th pulse is finished; predicting a driving frequency of an ON-time period T_ON(n+1) of an (n+1)-th pulse using a plurality of phase-shifted admittance values y' and corresponding driving frequency values obtained in the step of varying the driving frequency during the ON-time period T_ON(n) of the n-th pulse; and providing an RF output of the pulsed variable frequency RF generator at the predicted driving frequency f(n+1,1) in the ON-time T_ON(n+1) of the (n+1)-th pulse, wherein f(n,m) is a driving frequency in an m-th processing number in the ON-time period T_ON(n) of the n-th pulse, n denotes a sequence number of a pulse, m is a positive integer of 1 to q, and m denotes an index indicating the processing number of the control loop for varying a driving frequency in the ON-time period T_ON. a first step of measuring an RF current signal I and an RF voltage signal V at an output terminal of the pulsed variable frequency RF generator in the ON-time period T_ON(n) of the n-th pulse; a second step of calculating an impedance Zi and a reflection coefficient Γi at the output terminal of the pulsed variable frequency RF generator by using the RF current signal I and the RF voltage signal V in the ON-time period T_ON(n) of the n-th pulse, calculating a phase-shifted reflection coefficient Γ' from the reflection coefficient Γi to reflect a phase shift caused by a transmission line coupled between the load and the pulsed variable frequency RF generator, and calculating a phase-shifted admittance y' converted from the phase-shifted reflection coefficient Γ'; and a third step of selecting an increasing or decreasing direction of the driving frequency of the pulsed variable frequency RF generator depending on a sign of an imaginary part Im(Γ') of the phase-shifted reflection coefficient in the ON-time period T_ON(n) of the n-th pulse and varying the driving frequency, and repeating the first step, the second step, and the third step until the ON-time period T_ON(n) of the n-th pulse is finished; predicting a driving frequency of an ON-time period T_ON(n+1) of an (n+1)-th pulse using a plurality of phase-shifted admittance values y' and corresponding driving frequency values obtained in the step of varying the driving frequency during the ON-time period T_ON(n) of the n-th pulse; and providing an RF output of the pulsed variable frequency RF generator at the predicted driving frequency f(n+1,1) in the ON-time T_ON(n+1) of the (n+1)-th pulse, wherein f(n,m) is a driving frequency in an m-th processing number in the ON-time period T_ON(n) of the n-th pulse, n denotes a sequence number of a pulse, m is a positive integer of 1 to q, and m denotes an index indicating the processing number of the control loop for varying a driving frequency in the ON-time period T_ON.