PURPOSE: To provide an oscilloscope which enables selecting of an arbitrary field in a GCR8 field sequence to observe.

CONSTITUTION: A NTSC type video signal is quantized with an A/D converter 2 to fetch a part of a GCR signal into a waveform memory 3. In the fetching, a sweeping rate and a delay time are controlled with an address control circuit 7. An arithmetic circuit 8 analyzes the GCR signal to judge to which field the GCR signal belongs in a 8 field sequence. When the waveform of the field selected is brought into the wave memory 3, the waveform is taken into the waveform memory 3 and transferred to a display memory 4 to be shown on a tube surface according to the setting of the sweeping rate and the delay time of an operation panel 9.