A device (30) for preventing excessive insertion of a rod-like member (20) when the rod-like member is inserted into a gastrostomy catheter (10), and to a medical instrument provided with the same. The device comprises a reference position establishment part (31) which can be installed at a base end opening side of the gastrostomy catheter (10), a mobile part (32) which can be fixed to the endoscope (20), and a linking part (33). The linking part (33) can change the gap between the reference position establishment part (31) and the mobile part (32) within a range no greater than a set length, and links the reference position establishment part (31) and the mobile part (32). Furthermore, a bending instrument (40) for bending the tip end of the endoscope (20) when said tip end portion projects a prescribed length outwards from a through-hole of a stomach-internal fixed part is fitted to the tip end of the endoscope (20).
