A treatment device rotates a second rotation portion by operating an operation element, and switches between a first rotation position, at which the second rotation portion engages with the first rotation portion, transmits rotation motion to the first rotation portion, and transmits the driving force to the driving force transmission section, and the direction of the end effector relative to the distal end of the sheath is changed, and a second rotation position, at which the second rotation portion engages with the first rotation portion, restricts rotation of the first rotation portion, prevents the rotation motion transmitted to the first rotation portion, and prevent movement of the driving force transmission section, and a position of the end effector relative to the distal end of the sheath is maintained.
