A conduit switching piston 10 is provided that is fitted and inserted in an advanceable and retractable manner into a cylinder to which a plurality of conduits are connected, and is configured to switch communication states of the plurality of conduits. The conduit switching piston 10 includes: a shaft member 45； a flat portion that is formed along an extending direction E on an outer circumferential face 45g of the shaft member 45, and that has two edge portions facing each other on the outer circumferential face 45g and extending along the extending direction； a plurality of seal portions 53, 54, 55 and 56 formed having set intervals E1, E2 and E3 with respect to each other along the extending direction E on the outer circumferential face 45g of the shaft member 45, and configured to elastically contact an inner circumferential face of the cylinder； and a connecting portion 59 formed integrally with the seal portions 53, 54, 55 and 56 on the flat portion, and configured to connect the seal portions 53 and 54, the seal portions 54 and 55, and the seal portions 55 and 56 that are respectively adjacent along the extending direction E.
