An inserting instrument includes a first flexible tube section having a flexibility lower than a spiral tube, a second flexible tube section having a flexibility lower than the spiral tube and equal to or higher than the first flexible tube section in a state where the second flexible tube section is not covered with the spiral tube. The flexibility of the second flexible tube section is lower than that of the first flexible tube section when the second flexible tube section is covered with the spiral tube. The inserting instrument includes a third flexible tube section provided on the proximal direction side with respect to the second flexible tube section and having a flexibility lower than the first flexible tube section.
