coupling power transmission joint 70 which detachably couples an output shaft output part 55 a of the drive motor 55 with a rotating shaft 35 a of the pulley 35 is provided between the drive unit 50 and the treatment tool base part 20 the coupling 70 is for example a concavo convex fitting type coupling that can transmit rotary power the coupling 70 is constituted of a first coupling portion 56 that is provided on the output shaft 55 a side of the drive motor 55 and a second coupling portion 36 that is provided on the rotating shaft 35 a side of the pulley 35 when the treatment tool unit side base member 21 is coupled to the drive unit side base member 51 the first coupling portion 56 and the second coupling portion 36 are fitted to each other and are brought into a state where rotational power can be transmitted from the output shaft 55 a of the drive motor 55 to the pulley 35 fig5 is a perspective view showing the relationship between the displacement amount detected part 40 and the displacement amount detecting part 60 in the treatment tool m 1 of the embodiment fig6 is a cross sectional view as seen from arrow b b of fig5 as shown in fig5 and 6 the treatment tool unit side base member 21 is provided with a bracket 46 a sliding member 41 is attached to the bracket 46 via a sliding guide mechanism 45 the displacement amount detected part 40 is provided parallel to the sliding direction of the.