To provide a sawtooth wave generator which stably supplies sawtooth waves corresponding to a fluctuation in resonance frequency, and also to provide a sawtooth wave generation method.

The sawtooth wave generator 1 of this invention is constituted of a source frequency generation part 10 and a frequency generation part 20 for generating the frequency of reference signals, a sawtooth wave formation part 30 for forming the sawtooth waves on the basis of the reference signals, a voltage comparator 60 for comparing the voltage value of the sawtooth waves formed by the sawtooth wave formation part 30 with a preset voltage value, a phase comparator 70 for comparing the phase of the reference signals with the phase of the output signals of the voltage comparator 60, and a low-pass filter 80 for cutting the high band components of the output signals of the phase comparator 70 and feeding back the signals obtained by that to the sawtooth wave formation part 30.