Provided is a medical device designed to be inserted into a lumen of a living body, the medical device including: a long shaft part; and a cylindrical hollow body. The shaft part has a center axis at position which differs from a center axis of the hollow body on a cross section perpendicular to the center axis of the shaft part. The hollow body has a housing part extending along the center axis of the hollow body, the hollow body being a groove depressed from an outer peripheral surface to an inner peripheral surface or a slit penetrating from an outer peripheral surface to an inner peripheral surface. The shaft part is positioned between inner surfaces facing from the outer peripheral surface to the inner peripheral surface in such a way that at least a portion of the shaft part constitutes the slit or the groove of the housing part.