An insertion part to be inserted into the subject, a suction port 17 provided in the tip end surface 6S of the insertion part, a suction port 17 for sucking the liquid in the subject, a projection 40 projecting from the tip surface 6S in a columnar form, and a projection 40 facing the tip surface 6S, and a projection 40 is sandwiched between the protruding portions The passage 50 has a passage 50 provided in the projection 40 for passing the liquid positioned on the opposite side to the suction port 17 side.被検体内に挿入される挿入部と、挿入部の先端面6sに設けられた、被検体内の液体を吸引する吸引口17と、先端面6sから柱状に突出する突出部40と、先端面6sに臨んで吸引口17とは突出部40を間に挟んで反対側に位置する液体を、吸引口17側に通過させる突出部40に設けられた通路50と、を有する。
