a marker to be attached to an endoscopic treatment tool for precisely directing a tip of the treatment tool to a target site with no additional physical burden to the patient is provided . a marker 1 used in an endoscopic treatment tool to be inserted in a guide sheath , the marker including : a body 2 ; and a tip section 4 a for removably fixing the body 2 to a middle section of the endoscopic treatment tool , wherein the distance between the body 2 and a tip of the endoscopic treatment tool can be determined freely .