Provided are a spread spectrum clock generator and a spread spectrum clock generation method, a pulse pattern generator and a pulse pattern generation method, and an error rate measuring device and an error rate measuring method capable of improving usability when adjusting a waveform of a modulation signal during training. A setting screen 60 includes a 0-th frequency shift input unit 71 for arbitrarily setting a frequency shift of a waveform of a modulation signal in a plurality of time sections, a first frequency shift input unit 72, a second frequency shift input unit 73, a third frequency shift input unit 74, and a modulation selection unit 67 for switching a waveform pattern of the modulation signal from a first pattern to a second pattern.