PIPE LINE CHANGEOVER DEVICE FOR ENDOSCOPE

PROBLEM TO BE SOLVED: To provide a pipe line changeover device for an endoscope, which includes a piston capable of being easily mounted, and which certainly prevents waste of gas inside a cylinder in a natural state.SOLUTION: A gas supply/water supply changeover device includes: a cylinder including a connection port connected with a supply source side pipe line, and a connection port connected with a nozzle side pipe line; and a piston 81 fitted into the cylinder by insertion. The piston 81 includes: a piston body 82 having a first male thread 91m constituting a first fixing part 91; a first connection member 83 which has, at one end part, a first female thread 91f constituting the first fixing part 91 and screwed with the first male thread 91m, and at the other end part, a second male thread 92m constituting a second fixing part 92; and a second connection member 84 which has a second female thread 92 constituting the second fixing part 92 and screwed with the second male thread 92m of the first connection member 83. An inside diameter of the second female thread 92f is set to be an outside diameter of the first male thread 91m or less.