The objective of this invention is to provide a circuit that generates a spread frequency spectrum waveform with shaped frequency spectrum distribution. The waveform generator has a spread spectrum waveform generating circuit that generates a waveform with a spread spectrum and frequency spectrum distribution shaping circuit that shapes the frequency spectrum distribution of the spread spectrum waveform. In one embodiment, distribution shaping circuit can perform shaping such that the spread spectrum waveform has a frequency spectrum distribution having a spectrum reducing part in at least one band. Also, in one embodiment, the frequency of the spread spectrum waveform can vary periodically or nonperiodically.