A superconductive single flux quantum (SFQ) is an ultimate low power consumption electrical device. It can operate at a more than 100-GHz clock frequency with less than 1-uW power consumption per gate. A promissing application of the SFQ circuit in the near future is a real-time oscilliscope. With a real-time method, non-periodical waveform can be observed. This method is dispensable for future network monitoring, and higher sampling clock will be demanded. Commercially available semiconductor real-time oscilloscopes have extended input bandwidth and sampling clocks due to hardware and software interleaves. On the other hand, an SFQ circuit may increase those aspects without any interleaves because it can help implement a high-speed and high-reliable analog to digital converter (ADC) with its high-speed and periodic characteristics. We propose a new SFQ ADC and confirm its high sampling clock of over 150 GS/s by computer simurations.