A flow control valve has upstream fluid pressure outlets provided between inner and outer circumferential surfaces of an upstream retainer, which is attached to an upstream inner surface of a valve body. A second conduit is provided between inner and outer surfaces of the valve body on the upstream side of the valve body. First conduits are formed between the valve body and the upstream retainer. Downstream side fluid pressure outlets are provided between inner and outer surfaces of a downstream retainer, which is mounted to the inner surface of the valve body. A fourth conduit is provided between the inner and outer surfaces of the valve body on the downstream side of the valve body. Third conduits are formed between the valve body and the downstream retainer. A differential pressure sensor is attached to the outer surface of the valve body and to the second and fourth conduits.