A treatment instrument includes an insertion portion and a sample collection portion, wherein the sample collection portion includes a link portion and an advancing/retracting portion and when the advancing/retracting portion is located on a most proximal end side, the advancing/retracting portion and the link portion are connected in the axial direction and thereby become parallel to the insertion portion, when the advancing/retracting portion is located on a most distal end side, a part of the advancing/retracting portion and the link portion overlap and thereby become parallel to the insertion portion, and when the advancing/retracting portion is located between a proximal end portion side and a distal end portion side, the link portion is pushed out in a direction crossing the axial direction of the insertion portion by the advancing/retracting portion and thereby projects from the insertion portion.
