A high frequency power device includes a first oscillator outputting a first oscillating signal oscillated by a first predetermined frequency and a second oscillator outputting a second oscillating signal oscillated by a second predetermined frequency. A phase adjuster adjusts the phase of the second oscillating signal and a modulation index adjuster adjusts a modulation index of the second oscillating signal. A modulator outputs a modulated signal obtained by modulating, in frequency, the first oscillating signal by the phase adjusted and modulated second oscillating signal, and a high frequency output unit amplifies and outputs the modulated signal outputted from the modulator.