To provide an internal conduit structure of an endoscope that can prevent making a hole in a flexible tube made of Teflon (R) composing an internal conduit even when a puncture needle whose tip end projects from a sheath is inserted into the internal conduit.

The endoscope includes: a metallic straight pipe 25 mounted in an operation part 11; metallic non-parallel pipes 30, 33, 36 mounted in the operation part; a flexible tube 37 made of Teflon (R) mounted on the operation part and inside an insertion part; and a stopper groove 31 having a bottom formed inside the non-parallel pipes.