The present invention provides a fluid pipeline switching device. In the fluid pipeline switching device for an endoscope, when a piston is detached, contact between the filter and connecting holes formed on an operating cylinder can be prevented, thereby preventing filler damage. The fluid pipeline switching device is provided with the following components: a press button which is provided with a piston and a plurality of sealing components the operating cylinder which gradually necks in an insertion direction of the piston and is provided with the connecting holes connected with the fluid pipeline and a limiting member which is used for limiting the lower position of the piston. The plurality of sealing components gradually thins to the front end and separates the space in the operating cylinder along the axis direction. The diameter of the sealing component is smaller than the inner diameter of the upper segment of the segment of the piston, which is in slidable contact with the sealing component. Furthermore the positions of the connecting holes for connecting each fluid pipeline with the operating cylinder are closer to the front end than the lower-end position of the sealing components which slidably contact with corresponding components, thereby settling the task of the invention.
