PROBLEM TO BE SOLVED: To provide a sheath and a sheath dilator capable of reliably preventing misalignment between a dilator and a sheath while suppressing the component manufacturing costs.SOLUTION: A sheath for inserting a catheter into a fistula, comprises: a cylindrical sheath body； and a connector for holding one end of the sheath body. The connector comprises: a dilator for expanding the diameter of the fistula； and a holding member for holding the dilator when the sheath body is inserted into the fistula. In addition, the holding member is formed of a pair of gripping claws which are oppositely disposed along a direction orthogonal to a central axis of the sheath body.
