PROBLEM TO BE SOLVED: To provide an endoscope suction pipe line changeover device wherein local reduction of sealing efficiency occurring by a slide can be prevented and wherein high-accuracy machining for sealing is not needed.SOLUTION: In this endoscope suction pipe line changeover device 30, a cylinder member has: a first cylinder member 31 having a side face opening part 31c and a second cylinder member 35 detachably disposed above the first cylinder member 31. A piston member 37 has an opening part 39b, and a pipe line member 39a communicating with the opening part 39b. Sealing members 51 are disposed on the peripheral faces of the piston member, and performs the sealing above and below the opening part 39b corresponding to the side face opening part 31c of the first cylinder member 31, correspondingly to the inside diameter of the second cylinder member 35 smaller than the inside diameter of the first cylinder member 31.
