A flexible tube includes a helical tube having a first sparsely wound region, a closely wound region, a change region, and a second sparsely wound region. 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 such that the unbendability of the distal end portion of the third flexible portion is closer to the unbendability of the second flexible portion and the unbendability of the proximal end portion of the third flexible portion is closer to the unbendability of the fourth flexible portion.
