Provided are vesicles derived from bacteria belonging to the genus Proteus and a use thereof. The inventors of the present invention experimentally confirmed that the vesicles was significantly reduced in samples of patients with cancers, allergic-respiratory diseases, cardiovascular diseases, metabolic diseases, or neuropsychiatric diseases, as compared to that of normal people, and the vesicles inhibited the secretion of inflammatory mediators due to pathogenic vesicles and also exhibited anticancer efficacy. Therefore, it is anticipated that the vesicles derived from bacteria belonging to the genus Proteus, according to the present invention, may be usefully used for the development of a method of diagnosing cancer, cardiovascular diseases, metabolic diseases, neuropsychiatric diseases, allergic-respiratory diseases, and inflammatory bowel diseases, and a composition for prevention, treatment, and/or alleviation.