Inclusion: histologically or cytologically confirmed advanced or metastaticcolorectal cancer who had failed or are intolerant of oxaliplatin, irinotecan,and 5-FU. Patients with MSI colorectal cancer are not candidate for treatmenton this trial; adequate organ and bone marrow function; Exclusion:history of taking regorafenib or immune check point inhibitors;hypertension that is difficult to control (systolic blood pressure equal to 150 mmHg and diastolic blood pressure equal to 90 mmHg) despite treatment with several hypotensive agents;large amount of pleural effusion or ascites requiring more than weekly drainage;concurrent autoimmune disease, or a history of chronic orrecurrent autoimmune disease