This treatment tool is provided with: a first gripping member equipped with a heat-transmitting plate 13, which has a first surface 131 for contacting biological tissue and a second surface 132 that forms the reverse surface to the first surface 131, and a heater, which is disposed on the second surface 132-side and generates heat by being supplied with a current； and a second gripping member equipped with a facing member 16, which has a third surface 161 that, with the first surface 131, grips the biological tissue therebetween and a fourth surface that forms the reverse surface to the third surface 161, and a high heat conduction plate 17, which is disposed closer to the fourth surface-side than the third surface 161 in the facing member 16 and has a higher thermal conduction rate than the facing member 16. The width dimension in the short direction of the third surface 161 is longer than the width dimension in the short direction of the contact region Ar between the third surface 161 and the first surface 131. The high heat conduction plate 17 has points PN, which have the shortest distance to the contact region Ar in a cross-section perpendicular to the longitudinal direction, in regions to the outside of the contact region Ar in the short direction.L'invention concerne un outil de traitement pourvu : d'un premier élément de préhension équipé d'une plaque de transmission de chaleur 13, qui a une première surface 131 pour mettre en contact un tissu biologique et une deuxième surface 132 qui forme la surface inverse à la première surface 131, et un dispositif de chauffage, qui est disposé sur le deuxième côté de surface 132 et génère de la chaleur en étant alimenté avec un courant ； et un second élément de préhension équipé d'un élément de parement 16, qui a une troisième surface 161 qui, avec la première surface 131, saisit le tissu biologique entre elles et une quatrième surface qui forme la surface inverse à la troisième surface 161, et une plaque de conduction
