PROBLEM TO BE SOLVED: To provide an insertion device capable of safely obtaining desired pressing force to a lumen regardless of the internal diameter of the lumen and without being affected by the kinds of balloons.SOLUTION: An endoscope system includes: a balloon 8 provided on the distal end of an insertion part an air supply pump 14 for supplying liquid to the balloon 8 to expand the balloon 8 a balloon conduit 17 for connecting the balloon 8 to the air supply pump 14 to pass the liquid through a flowmeter 16 for measuring the flow rate of the fluid passing through the balloon conduit 17 per unit time to generate flow rate measurement signals including the measurement result of the flow rate a pressure detection part 15 for detecting the pressure of the fluid passing through the balloon conduit 17 to generate the pressure measurement signals including the measurement result of the pressure and a pressure control part 12 for drive-controlling the air supply pump 14 by using the flow rate measurement signals, the pressure measurement signals, signals of the estimated result which is obtained by performing calculation to estimate restoring force of the balloon 8 going to return to its original shape according to the kind of the endoscope system.
