To provide a high-frequency power supply device which can appropriately perform control for protecting an amplification part by surely detecting power values of fundamental frequency components included in progressive wave power and reflecting wave power.

In the high-frequency power supply device which supplies a high-frequency power obtained by amplifying a high-frequency signal S1 generated by a high-frequency generation part 101 to a load, a high-frequency signal S2 of a frequency f2 having a constant difference with respect to a frequency f1 of the high-frequency signal S1 is generated from a high-frequency generation part 102, the high-frequency signal S2 is multiplied by a progressive wave detection signal Sp and a reflecting wave detection signal Sr via multiplication parts 106, 110, and both detection signals Sp and Sr are converted into difference frequency signals having a constant difference frequency f1-f2. The power values of the fundamental frequency components included in the progressive wave power and the reflecting wave power are detected from levels of the difference frequency signals which are obtained by extracting the difference frequency signals by filtering, and an output of the high-frequency generation part 101 is controlled so that the total value of power values of fundamental frequency components does not exceed a limit value.