A treatment device includes an insertion portion, an end effector, a grasp portion, a transmitting member, a first locking portion, a second locking portion, and an operational body. The operational body is configured to switch between a first position where the transmitting member is moved forward along the longitudinal axis of the insertion portion to keep the end effector in a first state to extend along the longitudinal axis to the distal end of the insertion portion along the longitudinal axis, and a second position where the transmitting member is moved backward along the longitudinal axis of the insertion portion to keep the end effector in a second state to be rotated relative to the longitudinal axis with respect to the distal end of the insertion portion.