A helical tube of a flexible tube includes a first sparsely wound region which is cooperates with an outer sheath to form a first flexible portion, a closely wound region which forms a second flexible portion, a change region which forms a third flexible portion, and changing unbendabilities between a distal end portion and a proximal end portion thereof, and a second sparsely wound region which forms a fourth flexible portion. The change region changes an unbendability in cooperation with the outer sheath such that the unbendability of the distal end portion is closer to the unbendability of the second flexible portion and the unbendability of the proximal end portion is closer to the unbendability of the fourth flexible portion, in a state where the change region is arranged between the closely wound region and the second sparsely wound region. The change region changes an unbendability in cooperation with the outer sheath such that the unbendability of the distal end portion is closer to the unbendability of the first flexible portion and the unbendability of the proximal end portion is closer to the unbendability of the second flexible portion, in a state where the change region is arranged between the closely wound region and the first sparsely wound region.
