The tissue collection tool (1) has an elongated inner sheath (2) having a proximal end portion and a distal end portion and extending in the direction of the longitudinal axis, an opening portion and a bottom portion, and is disposed at the distal end portion, A first wire (10) which moves symmetrically away from the longitudinal axis to move away from the distal end so as to spread out the opening when moving forward from the distal end； a first wire 10), and in a state where the first wire (10) opens the opening portion, the extending portion (8) in contact with the bag body (3) on the bottom side of the opening end of the opening portion and the extending portion . 組織回収具（１）は、基端部と先端部とを有し長手軸の方向へ延びた細長い内シース（２）と、開口部と底部とを有し、前記先端部に配され、拡縮可能な袋体（３）と、先端部から前方へ移動したときに長手軸に対して対称的に離れるように移動して開口部を拡開する第一ワイヤ（１０）と、第一ワイヤ（１０）の間に配され、第一ワイヤ（１０）が開口部を拡開させている状態において、開口部の開口端よりも底部側において袋体（３）に接する延出部（８）と、を備える。
