An endoscope system sets a hardness variation of a thick flexible tube portion and a hardness variation of a thin flexible tube portion such that their respective ratios against base hardness are constant, and as each flexible tube portion becomes thicker, the hardness variation increases and an endoscope with a relatively thin flexible tube portion has a smaller hardness variation. This makes it possible to avoid situations like an endoscope with a thick flexible tube portion lacking hardness or an endoscope with a thin flexible tube portion becoming too hard, and makes it possible to perform optimum insertion operation in accordance with the thickness of a flexible tube.
