Plasma processing system

A high-frequency measurement unit includes a signal detector for detecting a high-frequency signal, and a calibration coefficient storage for storing calibration coefficients Cmin and Cmax used to calibrate a value Amin detected at the lowest limit frequency fmin and a value Amax detected at the uppermost limit frequency fmax to a proper measurement value Asmin and to a proper measurement value Asmax, respectively. The high-frequency measurement unit further includes a frequency detection unit for detecting a frequency fm of the high-frequency signal, a calibration coefficient calculation unit for calculating a calibration coefficient Cm for the frequency fm, and a calibration unit for calibrating the value Am detected by the signal detector to a proper measurement value Asm by using the calibration coefficient Cm calculated by the calibration coefficient calculation unit.