Immune checkpoint inhibitors which have been currently approved on malignant melanoma and non-small cell lung cancer in Japan, are having completely different mechanism from the conventional anti-neoplastic agents such as cytotoxic anticancer agents or molecular targeting agents. Therefore, although the response rate is not so high, the patterns of anti-tumor effect such as long-term survival or durable response and unique toxicity profiles to stimulate autoimmune response are quite distinguished. It has been found to be significantly different from conventional anti-neoplastic agents. The results of current clinical trials using immune checkpoint inhibitors for gastrointestinal tract cancers, promises to gain new promising treatment options near future. The clarification of the biomarkers and development of combination therapy is strongly warranted in the future.