An endoscope conduit switching device provided to an endoscope operating part, for switching between a fluid supplying state of supplying a fluid to a fluid ejection part via an ejection part-side conduit and a non-supplying state in a state in which a supply-source-side conduit communicated with a fluid supply source and an ejection-part-side conduit communicated with a fluid ejection part are connected and fluid is supplied from the fluid supply source, the endoscope conduit switching device provided with: a cylinder provided with a first connecting port and a second connecting port and a piston disposed so as to be able to slide in the cylinder and provided with a narrow opening formed along a longitudinal axis, a communicating hole for communicating the opening and the outside, a seal member provided on an external peripheral surface, and a first sealing valve and second sealing valve provided on either side of a through hole and further provided with an intra-cylinder first space in the cylinder, an intra-cylinder second space, a leak hole for ejecting gas to the outside that passes through the second sealing valve in a natural state, and a circumferentially directed recess positioned between the first sealing valve and the second sealing valve and communicated with a mouth of the through hole formed in an external peripheral surface of the piston disposed in contact with the internal peripheral surface of the cylinder.La présente invention concerne un dispositif de commutation de conduit dendoscope doté dune partie dactionnement dendoscope, pour passer dun état dapprovisionnement de fluide consistant à approvisionner un fluide à une partie déjection de fluide via un conduit latéral de partie déjection à un état de non approvisionnement, dans un état dans lequel un conduit latéral de source dapprovisionnement en communication avec une source dapprovisionnement et un conduit latéral de partie déjection en communication avec une partie déjection de fluide sont ra
