An endoscope 2A includes a flexible tube portion 3c provided on an insertion portion 3, a driving motor 45 having a driving axle 45a, an insertion assisting mechanism portion 30 configured to move by rotational driving force of the motor 45, and a driving shaft 50 insertedly disposed in the flexible tube portion 3c and configured to be rotated by the rotational driving force of the motor 45 to transmit the rotational driving force, for which first torsional rigidity in a state of being rotated in a winding direction is set higher than second torsional rigidity in a state of being rotated in an opposite direction. In a configuration in which the insertion assisting mechanism portion 30 selectively performs a first motion and a second motion requiring a larger amount of force than the first motion, the insertion assisting mechanism portion 30 performs the second motion by rotational driving force transmitted by the driving shaft 50 being rotated in the direction opposite to the winding direction around an axis.
