A bending instrument for an endoscope which is used when a fiberscope is inserted into a gastrostomy catheter. The bending instrument comprises a sheath which covers a fiberscope shaft of the fiberscope, and a bending member which allows the fiberscope shaft to bend together with the sheath. A light-transmissive window part is formed at the tip end of the sheath. Furthermore, the bending member comprises a fixed part which is attached to the tip end outer periphery of the sheath, a sliding part which is slidably attached further to the base end side of the sheath than the fixed part and which engages with a cylindrical engagement part of the gastrostomy catheter so as not to be able to go past an intra-stomach fixed part, and a linear linking part which links the fixed part and the sliding part.
