A switching valve assembly for an endoscope (10) includes a cylinder (50), a piston unit (51), a button device (43, 47), a flow channel (71, 72) in the piston unit, and plural flow openings (56, 57). The piston unit changes over plural flow lines (28, 46) between communication and interruption by changing a combination of the flow openings with the flow channel for communication. The switching valve assembly includes a cylinder cap device (76) and a slide device (77) of a cup shape. An end ring (96) keeps the slide device contained in the cylinder cap device. A first coil spring (78) is disposed between the slide device and cylinder cap device, for biasing the slide device in an upward direction from the cylinder. A second coil spring (79) is disposed between the button device and slide device, for biasing the button device in the upward direction with smaller force of bias than the first coil spring. The slide device includes an inner guide sleeve (104).
