A pipe changeover piston (10) fitted into a cylinder to which a plurality of pipes are connected so as to freely advance and retreat, and switching a communication state of a plurality of pipelines, the pipe changeover piston (10) extending to a shaft member (45) and an outer peripheral surface (45g) of a shaft member A planar portion formed along the direction E and having two edges facing each other on the outer peripheral surface 45 g and extending along the extending direction and a flat portion formed on the outer peripheral surface 45 g of the shaft member 45 in the extending direction E A plurality of sealing portions 53, 54, 55, 56 which are formed with mutual setting intervals E1, E2, E3 along elastic contact with the inner peripheral surface of the cylinder, A connecting portion 59 which is formed integrally on the flat portion integrally with the sealing portions 55 and 56 and which connects adjacent seal portions 53 and 54, 54 and 55, 55 and 56 along the extending direction E,複数の管路が接続されるシリンダに進退自在に嵌挿されるとともに、複数の管路の連通状態を切り換える管路切換ピストン10であって、軸部材45と、軸部材45の外周面45gに延在方向Eに沿って形成された、外周面45g上おいて互いに対向して延在方向に沿って伸びる2つの縁部を有する平面部と、軸部材45の外周面45g上において延在方向Eに沿って互いに設定間隔E1、E2、E3を有して形成されるとともに、シリンダの内周面に弾性的に接触する複数のシール部53、54、55、56と、シール部53、54、55、56と一体的に平面部上に形成されるととともに、延在方向Eに沿って隣接するシール部53、54間、54、55間、55、56間を連結する連結部59と、を具備する。
