A fluid passage valve is equipped with a valve body which is disposed rotatably through first and second shafts, a movable seat having a communication hole therein, and an elastic member that urges the movable seat toward a side opposite from the valve body. The first and second shafts are assembled and installed on the valve body such that an axis thereof is disposed at a position offset from a center of curvature of a spherical surface portion of the valve body. The fluid passage valve is placed in a valve-closed condition by the spherical surface portion abutting against a seating surface and closing the communication hole, and is placed in an open condition by the valve body separating away from the movable seat and thereby opening the communication hole.