The development of cancer immunotherapy is the history of activation of its immune system, however it is also the history of failure of the development of the therapy. In these histories, the concept of immune checkpoint was born resulting a big breakthrough. While many excellent fundamental researches have not reached clinical application, checkpoint inhibitors succeeded in translational research and drug discovery. Since anti-PD-1/PD-L1 blockade therapy has been delivered to the world, types of tumor were divided into two groups. One is sensitive type by immunotherapy called as Hot tumor, and the other one is the other way called as Cold tumor which is difficult to demonstrate effectiveness. In recent years it has become clear that the gut microbiota has a great influence in terms of tumor immune microenvironment. We are actively pursuing analysis of gut microbiota with cases of treatment by cancer immunotherapy and chemotherapy. The development of this research is boosted by improvement of the next generation sequencer and analysis method. In addition to this, we also add non-linear analysis by adding Artificial Intelligence (AI) to analytical methods. These results will be used for future fecal transplantation as a translational research. We introduce our new findings, explain the trend of the development of cancer immunotherapy in the world, and we will state what kind of action we are taking for it.