A robotic-assisted surgical system includes a flexible inserted portion having an elongated shaft a distal-end movement-amount detecting portion that detects an amount of movement of the distal end of the inserted portion an operating unit that is disposed outside the body and that is operated by an operator outside the body a driving portion that drives the inserted portion at a proximal end thereof in accordance with an operation signal input to the operating unit and a control portion that calculates a difference between the amounts of movement of the distal end and the proximal end of the inserted portion, and that, in the case in which the difference is greater than a predetermined threshold, controls the driving portion so as to notifies the operator to that effect.
