The present invention relates to a biomarker for evaluating or predicting response of a patient to metformin, and use thereof. The present invention relates to a composition and a kit for evaluating or predicting therapeutic response of a patient to metformin, comprising an agent capable of detecting one or more microorganisms selected from the group consisting of Blautia, Shigella and Clostridium. And, the present invention relates to a method for detecting one or more microorganisms selected from the group consisting of Blautia, Shigella and Clostridium from the sample of a patient, so as to provide information required for evaluating or predicting response to metformin.
