A flow control valve may include a case and a valve body axially movably disposed within a fluid passage defined in the case. The valve body may have an outer circumferential surface with a flow control surface. The valve body may further include a flange portion positioned on an upstream side of the flow control surface. The flange portion may include a sliding surface and a reference surface. The sliding surface may slidably contact a passage wall surface of the fluid passage. The reference surface may serve as a reference when performing configuration measurement of the flow control surface. The reference surface may extend within a first circumferential range about the axis of the valve body, and the flow control surface may extend within a second circumferential range about the axis of the valve body. The first circumferential range and the second circumferential range may at least partly overlap with each other.