It is intended to provide a sheath (1) for gastrostoma which comprises sheath body (11), into which a catheter (2) for gastrostoma is inserted, and a handle (12) and which is to be preliminarily inserted into a fistula in the case of inserting the catheter to the fistula and placing it in the body to thereby reduce the resistance against the insertion of the catheter for gastrostoma; a dilator provided with a sheath; a catheter kit for gastrostoma; and a method of dividing a sheath for gastrostoma. Use of the sheath for gastrostoma as described above makes it possible to reduce the insertion resistance in the case of placing a button type catheter for gastrostoma in gastrostomy or at the exchange of the catheter for gastrostoma. Moreover, it facilitates the air-supply control of an endoscope so that the endoscopic visual field can be stabilized in the course of operation.