Completion of atrial-appendage ligation using a ligation loop is confirmed easily and more reliably. Provided is an atrial-appendage ligation treatment tool including: an insertion portion that is introduced into a cardiac sac through a sheath penetrated through a pericardium a securing part that secures a distal end of the insertion portion to an atrial appendage and a sensor that is provided at the distal end of the insertion portion and that detects the state of the atrial appendage.
