A sleeve member of a movable unit has a first pressure receiving surface and a second pressure receiving surface. The first pressure receiving surface receives a first fluid pressure in an axial direction opposite to a biasing force of a spring, when a valve member closes a seat opening portion. The second pressure receiving surface receives a second fluid pressure in the same axial direction to a direction of the biasing force of the spring, when the valve member closes the seat opening portion. A first surface area and a second surface area are made to be equal to each other. Each of the first and the second surface areas is an area of a projected portion on a virtual plane perpendicular to the axial direction. Each of the projected portions is obtained when each of the first and the second pressure receiving surfaces is projected to the virtual plane.