This article presents a cost benefit analysis of AminoIndexTM Cancer Screening (AICS) in Japan. AICS is a new cancer diagnosis method based on profiles of amino acids. The cost benefit analysis is performed on each type of cancer, each sex, and each age class. The results indicate that AICS is cost-beneficial mainly for 50-75 years old for screening of several types of cancer including stomach, lung, and colorectal cancer. AICS is also cost-beneficial for younger female for screening of uterine-ovarian cancer.