An object of the present invention is to provide a conduit switching device for an endoscope capable of surely switching between a water supply state and an air supply state, and the endoscope conduit switching device of the present invention comprises a plurality A cylinder 31 (35) to which the conduit of the endoscope is connected, and a piston 32 (45) fitted into the cylinder so as to freely advance and withdraw, and the conduit for the endoscope In the switching device 13, when the piston is in the normal state, it is provided on one of the cylinder and the piston to elastically contact the other wall surface in order to isolate the gas circulation conduit from the outside among the plurality of conduits A sealing member 53 and leakage means provided on the other wall surface for releasing the gas circulation conduit to the outside after closing the liquid circulation conduit out of the plurality of conduits during the operation of releasing the state where the piston is pushed in 35 c.送水状態と送気状態とを確実に切り換え得る内視鏡用管路切換装置を提供することを目的とし、本発明の内視鏡用管路切換装置は、内視鏡1に設けられた複数の管路が接続されるシリンダ31(35)と、このシリンダに進退自在に嵌挿されたピストン32(45)とを有してなり複数の管路の連通状態を切り換える内視鏡用管路切換装置13において、ピストンが通常状態にある場合に複数の管路のうち気体流通管路と外部とを隔離するためにシリンダとピストンのいずれか一方に設けられ他方の壁面に弾性的に接触するシール部材53と、他方の壁面に設けられピストンが押し込まれた状態を解除する動作の途中において複数の管路のうち液体流通管路を閉塞させた後気体流通管路を外部に開放するリーク手段35cとを備える。
