The present invention relates to vesicles derived from genus Morganella bacteria and a use thereof, the present inventors experimentally confirmed that the vesicles were significantly decreased in clinical samples derived from patients with a malignant disease such as gastric cancer, colorectal cancer, pancreatic cancer, bile duct cancer, breast cancer, ovarian cancer, bladder cancer, prostate cancer and lymphoma, a cardiovascular disease such as myocardial infarction, cardiomyopathy, atrial fibrillation, variant angina, and stroke, diabetes mellitus, and Parkinson's disease as compared to normal persons, and the vesicles suppressed the secretion of inflammatory mediators by pathogenic vesicles and suppressed the occurrence of cancer, so that the vesicles derived from genus Morganella bacteria may be usefully used for the purpose of developing a method for diagnosing a malignant disease such as gastric cancer, colorectal cancer, pancreatic cancer, bile duct cancer, breast cancer, ovarian cancer, bladder cancer, prostate cancer and lymphoma, a cardiovascular disease such as myocardial infarction, cardiomyopathy, atrial fibrillation, variant angina, and stroke, diabetes mellitus, and Parkinson's disease, and a composition for preventing or treating the diseases or an inflammatory disease.