PURPOSE: To improve freedom in waveforms which can be generated to apply desired test waveforms without making software complicated by determining output time of a timing pulse with a period clock as reference.

CONSTITUTION: Timing information of test waveforms is stored in a pair of timing memories 1a, 1b, and a pair of timing generators 2a, 2b input the timing information. The information includes such information whether or not a timing pulse is output when a signal of a desired reference time is input and when the timing pulse is output if it is output. When the pulse is to be output, it is output after a predetermined time delay from the reference time, wherein as the reference time rise or fall of a period clock or time when ramp voltage of the period clock is below a constant time, etc. is employed. A waveform generator comprising an FF circuit 3 and a buffer 4 outputs test waveforms based on the pulse.