A high-frequency power supply device for outputting a high-frequency pulse to a target device based on a synchronous pulse and a clock pulse, comprising: a synchronous pulse generation mechanism that generates a synchronous pulse containing output level information and output timing information of the high-frequency pulse; an output level setting mechanism that generates an output level signal for setting an output level of the high-frequency pulse based on the output level information; an oscillation waveform setting mechanism that sends out a frequency setting signal and a pulse number setting signal respectively for setting an oscillation frequency and the number of pulses of the high-frequency pulse based on a phase difference between the synchronous pulse and the clock pulse; and an oscillation mechanism that receives a period reference signal of the synchronous pulse, the output level signal, the frequency setting signal and the pulse number setting signal to oscillate the high-frequency pulse, wherein the synchronous pulse generation mechanism comprises a synchronous pulse formation circuit that forms the synchronous pulse, a period reference signal generation unit that generates a period reference signal at a period reference time contained in the output timing information, the output level setting mechanism comprises a level determination unit (122, 222, 322) that determines an output level set in the high-frequency pulse in response to the output level signal, and a level setting signal generation unit that generates a level setting signal based on a result of the determination made by the level determination unit, the oscillation waveform setting mechanism comprises a synchronous pulse period detection unit that detects a period time in one period of the synchronous pulse; a phase difference determination unit that determines a phase difference between the synchronous pulse and the clock pulse at least in previous one period of the high-frequency pulse; and an output waveform parameter determination unit that computes an oscillation frequency and the number of pulses of the high-frequency pulse to be oscillated in the next period based on the period time and the phase difference to thereby send out an oscillation frequency signal and a pulse number signal, the oscillation mechanism comprises a clock pulse generator that generates the clock pulse based on the oscillation frequency signal, and an oscillation amplifier that receives the period reference signal, the level setting signal, the pulse number signal and the clock pulse to generate the high-frequency pulse based on these signals, wherein the output waveform parameter determination unit determines an oscillation frequency and the number of pulses in the next period for compensating the phase difference in the last period such that the phase becomes constant after a lapse of the period time of the next period. a synchronous pulse generation mechanism that generates a synchronous pulse containing output level information and output timing information of the high-frequency pulse; an output level setting mechanism that generates an output level signal for setting an output level of the high-frequency pulse based on the output level information; an oscillation waveform setting mechanism that sends out a frequency setting signal and a pulse number setting signal respectively for setting an oscillation frequency and the number of pulses of the high-frequency pulse based on a phase difference between the synchronous pulse and the clock pulse; and an oscillation mechanism that receives a period reference signal of the synchronous pulse, the output level signal, the frequency setting signal and the pulse number setting signal to oscillate the high-frequency pulse, wherein the synchronous pulse generation mechanism comprises a synchronous pulse formation circuit that forms the synchronous pulse, a period reference signal generation unit that generates a period reference signal at a period reference time contained in the output timing information, the output level setting mechanism comprises a level determination unit (122, 222, 322) that determines an output level set in the high-frequency pulse in response to the output level signal, and a level setting signal generation unit that generates a level setting signal based on a result of the determination made by the level determination unit, the oscillation waveform setting mechanism comprises a synchronous pulse period detection unit that detects a period time in one period of the synchronous pulse; a phase difference determination unit that determines a phase difference between the synchronous pulse and the clock pulse at least in previous one period of the high-frequency pulse; and an output waveform parameter determination unit that computes an oscillation frequency and the number of pulses of the high-frequency pulse to be oscillated in the next period based on the period time and the phase difference to thereby send out an oscillation frequency signal and a pulse number signal, the oscillation mechanism comprises a clock pulse generator that generates the clock pulse based on the oscillation frequency signal, and an oscillation amplifier that receives the period reference signal, the level setting signal, the pulse number signal and the clock pulse to generate the high-frequency pulse based on these signals, wherein the output waveform parameter determination unit determines an oscillation frequency and the number of pulses in the next period for compensating the phase difference in the last period such that the phase becomes constant after a lapse of the period time of the next period.