Spurious noise that occurs in the vicinity of a carrier can be removed even when a high-resolution cycle is set, thereby realizing low jitters in a high-precision variable clock signal. Cycle data that is set by a pattern generator in a waveform generation apparatus (a semiconductor test apparatus) is corrected in such a manner that spurious noise that occurs in a carrier of a high-precision variable clock is produced at a position far from the carrier in terms of frequency. As a result, the spurious noise can be assuredly removed by a phase-locked loop circuit, thereby realizing low jitters in the high-precision variable clock signal.